Light Tank M3A1/A3 Stuart in Yugoslav Service

Yugoslav Partisans/Socialist Federal Republic of Yugoslavia (1944-1960)
Light Tank – 56-100+ Received

The Yugoslav communist Partisans, or National Liberation Army, were one of the largest resistance movements against Germany in occupied Europe, fighting many hard battles against the Axis forces during WWII. The Allies, seeing the importance of this struggle (as large number of Axis troops were sent to the Balkans to quell the Partisans), decided to supply the Partisans with a number of American Stuart light tanks and other military equipment, such as armored cars, trucks, military uniforms, and small arms etc. These Stuart light tanks were not first to be operated by the Partisans (they had used tanks such as the Italian L3 or the French Hotchkiss H35 and SOMUA S35 tanks among others) but were provided in enough numbers to equip a Tank Brigade. This Brigade would see heavy fighting from late 1944 until the end of the war in Yugoslavia in May 1945. The Stuart tanks were important not just for the Partisans, but they represented the nucleus from which the future JNA (Yugoslav People’s Army) armored force would be created. The Stuart tanks would remain in operational service into the beginning of the 1960s.

Prelude

After the Italian defeats in North Africa and Greece, Mussolini had no choice but to seek help from his German ally. Hitler, unwillingly, decided to send German military aid to help the Italian conquest of Greece. For the planned occupation of Greece, Hitler counted on the neutrality of the Kingdom of Yugoslavia.
The government of the Kingdom of Yugoslavia joined the Tripartite Pact of Germany, Italy, and Japan on 25th March 1941. Two days later, Air Force General Dušan Simović, with the support of other military officers, staged a coup d’etat and overthrew the government (and the Regent Prince Paul) which had intended to join the Axis forces. The new government under Simović did not ratify the Tripartite Pact and commenced negotiations with Britain and the USSR. Due to these events, and in preparation for the attack on Greece and the Soviet Union, the German High Command decided to occupy Yugoslavia and create a safe environment for further operations. Thus began the ‘April War’ (codenamed Directive 25); the Axis invasion of the Kingdom of Yugoslavia on 6th April 1941.
After the end of the April War, Yugoslavia was divided amongst the Axis forces. Mostly because of the brutality of the occupying forces, the discontent of the occupied nations grew more and more. Very quickly in the territory of the former Kingdom of Yugoslavia, two liberation movements were formed, the Royalist Chetniks (Četnici/Четници) and the communist Partisans (Partizani/Партизани). The communist side would form the NOV (National Liberation Army) (Narodno-oslobodilačka Armija/Народно-ослободилачка Армија) but are more commonly and simply known as the ‘Partisans’.
These two groups at first cooperated together against the common enemy. In October 1941, joint Partisan and Chetnik forces attacked (with some captured German Beutepanzer SOMUA S35, Renault R35, and Hotchkiss H35/39 ) the city of Kraljevo (in southern-central modern-day Serbia). This attack failed and soon after, conflicting ideology would lead the former partners into an open civil war which would last until the end of WWII.

Axis invasion of Yugoslavia in 1941. The Axis forces used the southern parts of Yugoslavia, to quickly attack Greek positions. Source: Wikipedia

Forming of the First Tank Brigade

1943 was an important year for the Partisan movement for several reasons. Italy capitulated and the south of the country was occupied by the Allies. After the capitulation and withdrawal of Italian forces in September 1943, large parts of what was once Italian occupied Yugoslav territory were left undefended and abandoned. Partisans succeeded in capturing large quantities of weapons, including Italian tanks, self-propelled guns, armored vehicles, and trucks. The withdrawal of the Italians directly influenced the increase in the number of people who joined the Partisan side.
The communication and supply link between the German forces in Greece with the rest of Germany came under risk. The Germans were forced to send a large number of troops (14 division and 2 partly equipped divisions). The remaining German allies, the Hungarians and Bulgarians, were also heavily involved, with a total of 9 Divisions and 2 corps, with all available NDH forces (Independent State of Croatia/Nezavisna Država Hrvatska) and a number of Chetniks and Serbian collaborationist units also committed. In total, this combined force numbered some 1.1 million men (soldiers, support units and others).
Due to the fact that the Partisan movement was increasing in size and was tying down such a large number of enemy soldiers and equipment, they became an important factor in any future Allied war planning for this theatre of Europe. This was one of the many reasons why by the end of 1943 and early 1944, the Allies decided to support the Partisan movement only. Although they had also helped Chetniks in the past, due to the lack of Chetnik actions against the Axis forces in the Balkans (and many other factors which are under contentious and heated debate even to this day), they stopped any further assistance to this group. Thanks to the fact that the southern part of Italy was under Allied control, the possibility of closer cooperation with the Partisans opened up.
From 1943 and 1944 onwards, the Partisans liberated large territories that now had to be defended from any Axis attack. This led to the change of guerrilla-style fighting to a more direct one, but due to the increasing number of Axis forces, and more importantly the lack of a sufficient number of heavier equipment, these open battles were costly and not always successful.
The Allies decided to help the Partisans by training them and equipping them with much needed heavy weapons, such as tanks and aircraft. Many Partisan fighters that had some experience with this kind of equipment were transported to Italy to be used to form future training camps and centers. For the creation of the first tank unit with Allied equipment, 94 soldiers and officers in total from the 4th Tank Battalion (a unit that had been operating in Croatia and was equipped with captured Italian light tanks) were used. In April 1944, this group was transported by the Allies by sea to El Katadba in Egypt (near the city of Cairo). This group was reinforced with some 200 members of the Royal Yugoslav Army in Africa. This number would increase to 1,200, as most soldiers of the Royal Yugoslav Army would join this unit. By May 1944, it was moved to Chenifa (a training camp in Egypt), where the training of the crews would commence. The training was mostly carried out by British instructors and great attention was given to driving and firing. For training purpose, Stuart tanks and AEC armored cars were used. After some demanding and exhausting exercises, the training process was considered complete, and by late June, the unit was shipped to Italy once more. There, at Gravina Di Puglia (a village near the city of Bari), the First Tank Brigade was formed on 16th July 1944.
The British provided all the necessary materials needed to equip this brigade. At the very beginning, the Brigade had only 10 Stuart tanks. The British were at first reluctant to supply more tanks, as they did not believe that the Partisans could efficiently operate and maintain a larger number of armored vehicles. There were no more tanks available and the British could not provide personnel for maintenance of these vehicles. In order to discuss this issue, a meeting between the Supreme Allied Commander for the Mediterranean, General Sir Henry ‘Jumbo’ Wilson, and Josip Broz Tito (leader of the Partisans) took place on 10th August 1944. These negotiations were successful for the Partisan side and an agreement was made to supply a sufficient amount of armored vehicles to equip at least one tank brigade.

Stuart tanks and their crews prior to their transportation to Yugoslavia. The photograph was taken at Gravina Di Puglia in 1944. Source

Brigade organization

The original planned organization structure of this brigade was the following: It consisted of a headquarter company (with additional support staff), an ambulance company, four tank battalions, an engineering battalion, a company of armored cars, a mechanics company, and a unit for crew training (this unit was removed from the brigade very early on). Each of these four tank battalions was further divided into two tank companies (there is no precise information on how many tanks each had), an anti-tank battery, and a rear support company.
The Brigade unit’s fighting strength consisted of 56 light tanks, mostly M3A3 Stuarts (though there were a small number of M3A1’s and possibly even few M5’s), 24 AEC Mk. II Armored Cars, and two M3A1 ‘White’ Scout Cars (to be used as command vehicles). Support elements consisted of 21 Ford 3t trucks, 21 Chevrolet 3t trucks, 2 1.5t trucks, 8 Jeeps, 6 fuel trucks, two unidentified tracked vehicles, and 9 motorcycles. There is a chance that other vehicles were included, but these are not listed in the sources. This speculation is based on the fact that when the Brigade was transported to Yugoslavia it had 59 tanks, more than the official documented (which also complicates the task of determining the exact number of tanks used).
As there were not enough tanks to equip all four tank battalions, a decision was made to use only three tank battalions and one armored car battalion. This armored car battalion was never used as a whole unit, but was instead divided into smaller groups and given to the tank battalions to be mostly used in an anti-tank role, as the QF 6-pdr (57 mm) gun on the AEC provided strong firepower.
The anti-tank battery was equipped with towed 6-pdr AT guns, which was the same gun as on the AEC Mk.II Armored Car, allowing for ammunition crossover. For the purpose of towing these guns, trucks and two unidentified tracked vehicles (possibly Bren Gun Carriers) were used. The engineering battalion was only mechanized after the Partisans captured a number of vehicles, mostly German.
For supplies necessary for the functioning of the Brigade, the Allies supplied the Partisans with 29,000 liters of fuel (with additional 35,000 liters requested by the Partisans official), 12,000 liters of oil, 19,000 rounds for the 37 mm and 6-pdr guns, and some 220,000 machine gun rounds.
In total, the Brigade had some 1,619 men. The remaining soldiers that were not included in the Brigade were instead sent to the Soviet Union to be a part of the Second Tank Brigade.

The Light Tank M3 ‘Stuart’

The M3 light tank was designed in 1940 to replace the older and outdated M2 tanks that were in service with the American armored forces. The M3 had many improvements over the M2, including thicker armor, stronger (due to the increase in weight) vertical volute spring suspension with a rear idler wheel, increased speed, and improved firepower consisting of four .30 machineguns and a 37 mm cannon. The first series was powered by the gasoline-fueled (petrol) Continental seven-cylinder four-cycle radial aircraft engine, but after 1942, a new four-stroke diesel radial Guiberson A-1020 engine was used. It had a crew of four (driver, driver assistant, gunner, and commander). From March 1941 to August 1942, some 5,811 Stuart (with petrol engine) and 1,285 (diesel engine) were built.
The much improved M3A1 version was produced from April 1942 onwards. The first batches of M3A1 tanks were built by using riveted armor, but later models had welded armor. The changes that were made were: improved turret design (the small commander cupola was removed) with two hatch doors, reducing the number of machine guns to three on later built vehicles, and the addition of a turret basket. Some 4,621 M3A1 tanks were produced by February 1943, including a small number of diesel-powered tanks (around 211).
Soon after the M3A1, a new model, the M3A3, was made (the M3A2 was only a paper project) as a result of poorly designed frontal armor and small fuel capacity. The front and side armor of the Stuart M3A3 was angled and the front viewing hatch for the driver and his assistant were replaced by new overhead ones. The radio was moved from the hull to the turret rear. Due to extra space that the Stuart M3A3 now had, it was possible to increase the fuel capacity. This version was produced until August 1943 (when the production of the Stuart was finally canceled) with a total of 3,427 vehicles being built.
The Stuart series saw extensive operational service throughout the war on many different fronts. The USA supplied the Stuart series to other nations through Lend-Lease, including 5,532 (of all variants) to the British Empire, 1,676 to the USSR, 427 to Brazil, with several other hundreds going to China, France, the Netherlands, and many Latin American nations. Britain would subsequently give some of their Stuart’s to Yugoslav Partisans. By 1943, however, the M3 was already outdated, due to its weak gun and feeble armor.

Partisan Stuart tanks in combat

Author’s note: as the sources often do not specify the exact model of M3 tank used by the Partisans (it could be either M3A1 or M3A3 or even M5), this article will use the Stuart designation for the sake of simplicity, unless the sources specify which model or version. Also, note that the Partisans and later in JNA documents designation Stuart was wrongly written as ’Styart’ or ‘Stuard’.
The Brigade was transported by British ships to the island of Vis (off the Yugoslav Adriatic coast) in early September 1944. This operation was successfully completed by October. Immediately after, all elements of the Brigade were transported onto Yugoslav mainland and were divided into two groups: Northern and Southern.

The Northern Group

The Northern Group (the 2nd Tank Battalion and half of the 3rd Tank Battalion, in addition to AEC Mk.II armored cars which were equally divided to reinforce the 3rd Battalion in both groups) was tasked with helping other Partisan units in fighting and expelling the German (118th Jagerdivision) near the island of Brač (in the south of modern day Croatia). For this operation, 34 Stuart tanks and 12 AEC Mk.II armored cars were chosen. The transportation process on behalf of the British was slow, and by the time the 2nd Battalion was ready for action, the Germans forces had been driven-off. The next step was to transport these units to the mainland, but there was a problem due to the insufficient number of adequate Partisans transport ships. The British refused to help because of enemy coastal artillery. The Partisans however, decide to attempt to land by using all ships they could find. By late October, most tanks were transported onto the mainland, with only one tank being lost as a consequence of heavy German artillery fire. This group, along with other Partisans forces, pursued the retreating German forces. The progress was slow due to obstacles and mines which had been placed by the Germans. By late October, Partisans broke through the German defense line (Solin-Kaštel-Sučurac). In the night of 27th-28th October, a group of four Stuart tanks were sent to attack retreating enemy forces, but in this attack one Stuart tank was lost to enemy fire.

Transportation of a M3A3 tank by a British ships. Source: https://www.znaci.net/arhiv/fotografija/12063
After securing the coastline, the Northern group was moved toward the city of Šibenik (in central Dalmatia). It was planned by the Partisan high command to attack the city from two sides. Expecting a larger attack on the city, the German began withdrawing their forces (there was some number of Chetnik forces helping defend the city). During the advance on the city, elements of the Second Battalion unexpectedly came across a German force, and after some fierce fighting, lost four Stuart tanks with most of their crews being killed. The Germans had a battery of 75 mm PaK 40 anti-tank guns which could easily destroy Stuart tanks. There were other skirmishes with both German and Chetnik forces. A group of Chetniks came across a column of Stuart tanks, incorrectly thinking they were German tanks. The Partisan tanks immediately opened fire, killing many while the rest surrendered. Some German forces were left behind during the retreat and were surrounded. All available tanks and armored cars in the region were sent to destroy this group, but after some intense fighting, they failed and lost four tanks in the process, with one falling off a cliff. Consequently, the Germans managed to fight through the Partisans lines and escape. Regardless of this, the city of Šibenik was captured on 3rd November 1944.
Before the war, Šibenik had been a large naval shipyard and possessed a number of workshops. For this reason, the Partisans (despite some heavy sabotage made by the German) chose to make a repair and maintenance facility there. The Partisans managed to salvage some facilities and trained personnel in repairs and maintenance. As there was no reserve of new tanks, all tanks were considered important. Vehicles which had been destroyed or damaged were transported to Šibenik (how this was done is unknown, though possibly other tanks were used for towing) to be repaired if possible or to be used for spare parts. Those with turrets damaged beyond repair were used for different modifications equipped with captured German weapons. Šibenik would remain the main base for repairs and maintenance until the end of the war. In November, a tank school was moved to Šibenik from Gravine in the south of Italy to train new personnel. Training was mostly carried out on captured vehicles such as French and Italian tanks.

Šibenik was an important repair facility for the Partisans. Here we can see an M3A3 being repaired. As a number had lost their turret, they were reused for mounting captured German guns. The photographed vehicle could be one of those. Source

Collection of tanks of the Northern group at Šibenik, Winter of 1944/1945. Source
The next vital city to capture was Knin (on the Zagreb-Split road in inner Dalmatia). It was defended by a large force of entrenched German troops supported by Croatian Ustasha (Ustaše/Усташе), and Chetnik units, consisting of some 20,000 men, 20 tanks ( French Hotchkiss H35/39 and Italian FIAT (possibly) L6/40 tanks – under German flag). The Brigade’s Northern group was tasked in supporting other Partisan units (26th and 19th Divisions) in taking this city. The Brigade was further divided, with 13 tanks and 6 armored cars being assigned to the 26th Division and 12 tanks and 5 armored cars being assigned to the 19th Division. On 25th November, the first attacks using tanks and armored cars were unsuccessful, resulting in the loss of one tank and one armored car. The Brigade’s vehicles were not used as a single entity, but were instead divided into even smaller combat groups to support infantry units, which limited their offensive power. Furthermore, due to their tactical usage, the vehicles were easy targets for the defending forces. The armored vehicles were withdrawn and sent to support the attack of the 1st Dalmatian Proletarian Brigade on the city. The attack began on 2nd December, and after some heavy fighting, the Partisans managed to break the German resistance, which forced them to abandon Knin. By 4th December, all retreating German forces were destroyed or forced to surrender. The battle for Knin had been bitter and bloody, with the Partisans losing four Stuart tanks and one AEC armored car.

Actions of the Southern Group

The second Southern group (1st Battalion and the remaining elements of the 3rd Battalion) was tasked with the liberation of the Mostar region, which was vital to the Germans, as this was the main line of retreat for their remaining forces in Greece. Prior to the arrival of the Stuart tanks, Partisan forces had been stopped at the village of Buna (modern-day Bosnia). It was well defended, and the Neretva River flew through it, giving an extra obstacle that the Partisans had to overcome. Partisans with support of Stuart tanks and anti-tank guns attacked these positions but were not able to break through. The Stuart crews had great problems with the unknown terrain, with two being bogged down and a third falling on its side, forcing the crews to abandon the vehicles. Even though there was a danger that the Germans would destroy them, the Partisans went to great effort to salvage them. The Germans then launched a counterattack using Italian tanks which drove the Partisans back and brought a local Partisan hospital into danger. To save the situation, a tank company was quickly sent to try to stop the German advance. The counterattack was successful and drove the German back, with the loss of a single Stuart tank.
The next Partisan move was to attack the city of Široki Breg, which was a strong forward defense position defending Mostar. For this attack, 3 Stuarts and 3 AECs were chosen. But this attack proved unsuccessful, as the commander of the leading tank ran into (what he assumed was) a minefield. Instead of moving to another position, the commander decided to wait for infantry to clear the way for him. His tank was spotted by the Germans who immediately opened fire, hitting the tank, which caught fire, forcing the rest to withdraw. The next attack was also unsuccessful.
Using another similar force, the Partisans attacked another strong point at Nevesinje. The attack began on 30th November with three Stuart tanks and one AEC armored car with infantry support. The attack started well, but it was stopped as the Germans had six tank (four Italian, and two German tanks which the Partisans identified as ’Panthers’) and a number of Flak 3.7 cm guns. In the following battle, the Stuarts proved to be no match against the German tanks and one was lost, with one AEC receiving three direct hits, but miraculously, despite the damage, managing to pull back. The Germans lost one of their FIAT tanks. These actions were mostly unsuccessful due to the inexperience of the crews and commanding officers, poor positioning, insufficient scouting, and the use of tanks individually in a fire support role.
The fighting for Mostar continued until January 1945, when the Germans and their allied Croatian forces launched attacks on two bridges over the Neretva river in the hope that their destruction would slow down any future Partisan attack. One bridge near the city of Čapljina was briefly captured, only to be recaptured by Partisan forces with the help of several Stuart tanks (the bridge was damaged but still in use). Three Stuarts were damaged, though the Germans claimed five or more had been damaged. Two were captured by the Germans and used against the Partisans, with one later being destroyed in February and the second being recaptured. This indicates that the Partisans lost more than three tanks.

Unification of the Two Groups

As the Southern group alone proved insufficient to take down Mostar, the Northern group was called in to help in the upcoming planned offensive. Total Partisan strength was around 40,000 men, while the Germans (with Chetnik, Ustasha and a small numbers of Italians) had some 20,000. The Northern group made a 186 km long journey to reach its destination. On this journey, five Stuart tanks had to be abandoned due to mechanical breakdowns but would later be recovered.
At this time, the Brigade was reformed. As both groups had used the armored cars to reinforce the split 3rd Battalion, the Brigade HQ made the decision to rename the 3rd (Northern Group) into the 4th Battalion, as it was deemed that its dissolution would affect the battalion’s efficiency given that it had proved to be an effective force. As there were no spare British vehicles to equip this unit, enemy captured vehicles were used (exact models are unknown but possibly French – one Panhard 178 was used – or Italian).
The first attack with the reunited Brigade was launched against Široki Breg (6th February 1945), which was defended by a force of between 6,000 and 7,000 men equipped with different caliber anti-tank guns (37 mm to 75 mm). The attack was led by a group of Stuart tanks, while the AEC armored cars provided fire support against pillboxes and anti-tank guns, both being supported by Partisan artillery fire. But there was confusion as to how to proceed when the leading tanks ran into a minefield. Five tanks were lost to enemy fire and the attack was called off. All tanks were recovered, but at a great loss of life (eight killed and twenty-two wounded). Partisan high command decided to attack from the south with the 3rd Tank Battalion. Fortunately for them, due to the uneven terrain, this part of the defensive front was poorly defended and there were fewer mines and anti-tank guns. The attack was successful, which led to Germans leaving the first line of defense and pulling back into Mostar. A number of enemy armored vehicles were captured (at least one Somua S35 and one Semovente 47/32).

One Stuart M3A3 during the fight for Široki Breg in 1945. Source
The main attack began on 13th February with the support from the tanks from the 2nd and 3rd Battalions. After some fighting and navigation through bad terrain, they finally managed to cross three bridges and enter the city. Partisans also attacked from Nevesinje, with progress being slow due to the terrain, but they eventually managed to enter the city. German forces managed to escape toward Sarajevo, but with great losses. The Brigade had only lost one Stuart in addition to four damaged tanks.

At the battle for Široki Breg, even the Stuart M3A3 armed with the German 7.5 cm PaK 40 was used. Source: https://znaci.net/arhiv/fotografija/14367
The First Tank Brigade was later involved in supporting a large Partisan force of some 70,000 men against German and Croatian forces (20,000 men and 20 tanks) located in western Bosnia and the Croatian coast. The Brigade was again divided into two groups: the 1st and 3rd Battalions were given to the 26th Division and 2nd and 4th Battalions to the 19th Division. This was done by the Partisan HQ due to previous experience and cooperation of these forces. The 19th Division was tasked with capturing the city of Bihać (modern-day northern Bosnia). This Division was supported by Stuart tanks which made good progress, and after a few days of fighting, forced the German to pull back to the city. Two tanks were damaged, one by mine and one by a grenade. The advance was temporarily stopped as the Germans placed many mines and obstacles in the way, so the tanks had to wait for pioneers to clear the way. After the road was cleared, the advance carried on. As they approached the city, two AEC armored cars were sent to capture an intact bridge, but as they were crossing it, the Germans blew it up. One AEC dropped into the river, with the second one being destroyed by the Germans. The Germans, not willing to lose the city, sent reinforcements. To counter this, the 1st and the 2nd Tank Battalions were sent into the fight. The enemy was stopped at the cost of two Stuarts from the 2nd Tank Battalion. The 1st Battalion engaged heavy enemy resistance and lost 3 Stuarts with an additional one being damaged. As the battle was turning against them, the German and Croatians began a withdrawal. During the battle and retreat, they lost nearly 14,000 men. The First Tank Brigade suffered heavy losses. Out of the original 43 tanks, 8 Stuarts and 2 AEC’s were lost with an additional 7 Stuarts being damaged. Partisan mechanics worked day and night to repair as many of them as they could.
The Partisans continued to move towards the west, reaching the city of Gospić in what is today southern Croatia. On 4th April, the attack lead by the First Tank Brigade and five infantry divisions began. To counter this advance, the German sent 10 tanks (Italian L6-40). The Germans lost two tanks and had to pull back. After that the German defense was breached, they began to withdraw. One Stuart was destroyed and another damaged by enemy anti-tank fire. German and Croatian forces sent to stop them were beaten back. The Germans and the Croatian allies lost some 4,000 men, 40 guns and 20 armored vehicles.
The 2nd Tank Battalion was sent to capture Tounj (a small town southwest of Zagreb). Capturing this city would prevent German withdrawal from western Bosnia. The attack began on 13th April, and after a few days of heavy fighting, it was captured. Only one Stuart was damaged. Allegedly, one ‘Panther’ tank was destroyed by two AEC armored cars. This vehicle was proven later to be in fact a StuG III.
The final operations were the battles for Rijeka and Trieste, in the very west of Yugoslavia. The German positions were heavily defended with three defense lines consisting of a large number of old and new bunkers with 88,000 men, 338 guns, 60 tanks and 15 armored cars defending it, supported by Italian, Croatian and Chetnik forces. The total strength of the Partisan 4th Army (which had charged name before the attack) was 90,000 men, 366 guns, and 80 armored vehicles, counting with the support of the British RAF. The 4th Tank Battalion was the first to see action (17th April) in an unsuccessful attempt to subdue the defenders of the city of Sušak. The tanks proved useless in the attack on the well-defended city. The city was liberated on 21st April. In following days, two Stuarts were destroyed in addition to another one being damaged. By end of April, four Stuart tanks were cut-off and surrounded by German forces. The crews dismounted their tanks and used the Stuart’s machine guns to make a defensive perimeter whilst the gunners fired the main guns in support. The next day, Partisan infantry broke the German line and the Stuarts were saved. Due to bad terrain, tank use was limited, and one Stuart was lost on 28th April. Finally, by 3rd May, the line was broken and the city Rijeka was taken.
The city of Trieste was one of the last German resistance lines in this region. For its taking, the 2nd and 4th Tank Battalions were chosen to support the infantry divisions. The attack was carried out in two directions (each supported with one Tank Battalion). The 4th Battalion advance was successful, which led to the capturing of large stockpiles of ammunition and other war materiel near the village of Sežana. The second column was stopped as the bridge leading to Škofije was destroyed. This column was instead moved to Sežana to join forces with the 4th Battalion. This force managed to destroy many German units which were retreating in that direction. The battle for Trieste began on 30th April. German resistance was heavy and the first Partisan attack was repelled. On the same day, the 2nd Tank Battalion fought for the village of Basovizza, which was defended by 12 German tanks (including unknown numbers of captured Soviet T-34/76’s). During the following skirmishing, the Germans lost two tanks, with one T-34/76 being destroyed by an AEC armored car.

Advance on Trogiro of the First Tank Brigade in 1945. Source
The war for the Germans was all but lost. They continued to fight stubbornly to defend their last defense line at Trieste. The 2nd and 4th Tank Battalions were involved in liberating Trieste. As the Partisan attack was too strong, many Germans tried to flee by boat to Venice. Most boats were sunk by the guns of the Stuart tanks. By 2nd May, the battle was mostly won bar a few pockets of German resistance, which, with the help of the Stuart tanks were eliminated. By 3rd May, the last German resistance was crushed.
The last action of the First Tank Brigade was at the city of Rijeka, near Trieste, where large numbers of Germans were retreating to Austria. The 1st Tank Battalion was the only battalion available, but its tank forces had been depleted. The first attack on the German positions was unsuccessful, with the loss of four Stuart tanks. The Partisan HQ’s, after the capture of Trieste, moved large forces to this area. By this time, the 1st Tank Battalion had only a few operational tanks, and was not able to stop the German advancing forces. The 2nd and the 4th Tank Battalions arrived, but even they were hard pressed by the now desperate Germans. Two Stuart were lost on the night of 6th-7th May. Seeing that there was no hope of breaking out, the German Commander, General Kibler, unconditionally surrendered to the Partisans.

Small numbers of the obsolete M3A1 Stuart light tank were sent to the Yugoslav Partisans.

Most of the Stuarts supplied to the Partisans were the improved M3A3 version with sloped armor.

One M3A3 Light Tank which had a damaged turret had it replaced with a 20 mm Flakvierling.

Another M3A3 Light Tank that had its turret or its armament damaged was modified to carry the potent 75 mm Pak 40 AT gun.

Fictional illustration of a Partisan 15 cm sIG 33 gun mounted on an M3A3 chassis. Such a vehicle was allegedly converted, but there is no proof to back this claim.

Fictional illustration of a Partisan M3A3 Stuart armed with a 120 mm Granatwerfer 42 mortar. While some sources claim this vehicle exists, there is no proof to back its existence.
Illustrations by David Bocquelet with modifications by Leander Jobse.

Even though most tank used by the 1st Tank Brigade were M3A3’s, smaller numbers of older M3A1 (second tank in the column) were also used. This photograph was taken near Molmino in early 1945. Source

Total losses and reasons for them

By the end of the war, the First Tank Brigade had suffered heavy losses, with 33 tanks and 5 armored cars being destroyed, with a further 31 tanks and 2 armored cars being damaged. The Partisan tank losses were high as the Germans were using well-trained infantry (especially in the use of anti-tank weapons, such as the Panzerfaust and explosives), a lack of coordination with infantry, the inexperience of the crews, lack of adequate scouting, and difficult terrain. Poor and inadequate coordination with infantry were the reason why many tanks were lost. The infantry often lied to the Stuart tank crews of the presence of German anti-tank positions. They were hoping that the tank crews would somehow spot enemy anti-tank weapons and destroy them. This practice forced the Partisan High Command to give special orders forbidding this kind of actions. Another problem was lack of reconnaissance, as the ordinary infantry reports were not always the most reliable as seen earlier.

After the war

In June 1946, the total number of Stuart tanks was 54 (two of which were locally converted Flak Stuart’s). The First Tank Brigade was (from 1946) equipped with Soviet T-34/85 tanks and the Stuart were passed on to the 6th Tank Brigade. In later years, they were used mostly in military parades or as training vehicles. They remained in use by the Yugoslav People’s Army until 1960.

When they were finally withdrawn from operational use most were scrapped. Because of the historical significance these tanks had for the JNA, it was decided to preserve a certain number of them. Two Stuarts (one M3A1, serial number ‘8770’, and one M3A3, serial number ‘8776’ ) were placed at the Belgrade Military Museum (Serbia). One was placed as a monument in the Serbian city of Kraljevo. Three can be found in Bosnia and Herzegovina (BiH): one M3A1 in Sarajevo and two (M3A1 and M3A3) in Banja Luka. Two others (M3A1 and M3A3) are in Slovenian Military Museum in Pivka. The M3A1 in Pivka was bought from the Brazilian Army by a private collector before being given to the museum in 2008.

The M3A1 at the Belgrade Military Museum Source: Wikipedia

The M3A3 at the Belgrade Military Museum Source: Wikipedia

The M3A3 in Kraljevo. Source

The M3A1 (serial number ‘6739’) from the Sarajevo (BiH) National Museum. Source

The M3A3 in Banja Luka. Source

The M3A1 and M3A3 in the Pivka Museum Slovenia. The M3A1 (to the left) was originally in the Brazilian army. Source

Color and Markings

The Stuart tanks supplied to this Brigade had the original British continental green color, though a small number of tanks were painted in desert yellow or even combinations of both camouflage schemes.
Marking-wise, all tanks had the Yugoslav tricolor Flag (red, white and blue) with a red star in the middle painted on the hull side. Sometimes, a small red star was also painted on the turret. Political slogans (Za Zagreb-toward Zagreb) and the names of some cities (Beograd-Београд, Ljubljana-Љубљана etc.) were often written on the tanks, especially towards the end of the war.

How Many Were Supplied?

Although at first glance it seems that the number of Stuarts supplied can easily be determined, this is not the case. What is known with certainty is the fact that the British forces during the foundation of the First Tank Brigade supplied it with 56 M3A1/A3 tanks. It is possible that a few M5 were also included in this, but there is little or no evidence of this.
Authors Bojan B.D. and Dragan S. cited that on 6th March 1945, additional 36, mostly older, M3A1’s were supplied to the Partisans, with a few more in April. Additionally, three more tanks (abandoned by the Allies) were repaired by members of this brigade before their shipment to Yugoslavia.
According to Aleksandar R., some 51 tanks were supplied to replace the damaged and destroyed during the war. It is a possibility that an unknown number of tanks were supplied in small quantities by the end of the war.
The author Dinko P. presents several interesting facts:

• When the Brigade was transported to the island of Vis, it had 59 tanks (here he agrees with Bojan B.D. and Dragan S.).
• He also found information for additional M3A1/A3 tanks supplied on several occasions in Yugoslav official documents, but the exact number of vehicles are not mentioned.
• The author was able to talk to a soldier from the First Tank Brigade (who had been part of it since the very beginning of the Brigade). According to him (the name of this soldier is not mentioned), all vehicles that were given by the Allies were operated in this unit, including the ones used for training. These (that were used for training) were transported by Partisan ships after the original transfer (by the Allies) of the Brigade to the territory of Yugoslavia. Also, an unknown number of tanks were ’obtained’ in various (and suspicious) ways, aka they stole them intact or slightly damaged from Allied army depots. In these cases, the Allies decided to turn a blind eye and did not prevent the Partisans from doing this.
• On 31st January 1945, the total number of M3A1/A3 is listed to be 60 tanks, which is a bit more than the original number of 56 tanks.
• Registration numbers and British labels (which were not removed in most cases) on a number of tanks give some indications that these vehicles were not originally intended to be supplied to the Partisans, but somehow these tanks found themselves in Yugoslavia.

According to Leland N., the British had supplied the Partisans with 52 M3A3 tanks with an additional 40 in the first half of 1945. Author Steven J, Zaloga writes that one M3A1 and 56 M3A3 were supplied.
Determining the exact number of supplied vehicles is more complicated given the fact that a fairly large number of damaged tanks were salvaged and put back into action. These vehicles could possibly be mistaken as newly supplied ones, and thus give a wrong impression of the total numbers. So, according to these facts, the total number may range from the original 56 to 100, or even more.

Partisan Stuart modifications

During the heavy fighting for the liberation of Yugoslavia, several Stuart tanks were damaged. Given that the caliber of the main gun on the Stuart tank was inadequate for a successful anti-tank role, the partisans decided to try to mount some captured German weapons in order to increase their firepower.
By the end of 1944, in Šibenik, the Partisans set up a workshop to repair their vehicles. In addition to the workshop, a collection office (also located in Šibenik) for captured, damaged, and destroyed vehicles was set, which also served as a source of spare parts. There, damaged M3A3 tanks were modified and armed with German weapons, such as the 75 mm PaK 40 anti-tank gun and 20 mm Flak 38 Flakvierling. It is also alleged that the Partisans rebuilt two more tanks and armed one with a mortar and the other with a 15 cm sIG 33 heavy infantry artillery gun, but the existence of either of these vehicles cannot be ascertained at this time. It is also worth mentioning that a single Somua S35 was rearmed with the 6-pdr gun taken from a damaged AEC armored car.
A final note is that most, if not all, British supplied Stuart tanks had track mudguards. The Partisan tank crews began removing them early on as they were a hindrance during tracks repairs.

Light Tank M3A3 with 7.5 cm PaK 40

As the 37 mm main gun was almost useless against stronger armored vehicles, the powerful 75 mm PaK 40 was installed on three Stuart tanks. The upper structure mounted the 75 mm PaK 40 anti-tank gun with its twin layer gun shield of 4 mm (0.16 in.) thick steel and a small armor plate between the gun and the tank hull in addition of two side armored plates.
One such armed Stuart managed to destroy a German T-34/76 in April 1945. Installing this gun made these vehicles capable of destroying any tank on this front. Drawbacks of these modifications include, among several others: slim armor, high recoil when firing the gun, low ammunition capacity.

One 75mm PaK 40 armed Stuart during the Battles for Trieste and its surroundings in May 1945. Source 

Light Tank M3A3 with 20mm Flak 38 Flakvierling

On two damaged M3A3 tanks, the German 20 mm Flak 38 Flakvierling anti-aircraft gun was installed. The only armor protection for the gun operators was the front gun shield, with no side or rear armor. This vehicle would be mainly used in the role of fire support for ground troops. The immense rate of fire of their Flakvierling armament was used to suppress enemy infantry, unarmored vehicles, and anti-tank positions.
The reasons for building these two modifications are not clear, as there were only a limited number of German and their allied planes flying over Yugoslavia by the end of 1944 and in early 1945. Both vehicles survived the war and continued in use for some time, possibly as long as up until the sixties.

Two Stuarts were armed with German 20mm Flak 38 Flakvierling anti-aircraft gun. They were possibly used in combat but there is no information about their actions. Both vehicles would survive the war. Source

M3A1/A3 Mortar

Allegedly, during the war, one or two mortars were mounted on a Stuart chassis. The caliber of these mortars could be either 81 mm or 120 mm. One of the main ‘culprits’ for this confusion is a picture published (possibly after the war or just before its end) that shows Partisan crews using a vehicle which is assumed to be an M3A1/A3 as the base armed with two 120 mm mortars. However, this is not true, as the vehicle was, in fact, a German Sd.Kfz. 251 Ausf. D half-track armed with twin 120 mm Granatwerfer 42 (which is basically a direct copy of the Soviet M1938 without any changes to it). It is not known whether it was a Partisan modification or if they had captured this vehicle from the Germans (the second option is the most likely). So it is very likely that such a vehicle based on the M3A1/A3 did not exist.

Both pictures are taken in Šibenik. The first allegedly shows the M3A1 armed with two mortars, while the second picture shows that it is actually a German Sd.Kfz. 251 Ausf.D half-track. Source

M3A1/A3 with 15 cm schweres Infanterie-Geschütz 33 (15 cm sIG 33)

The existence of the 15 cm schweres Infanterie-Geschütz 33 (15 cm sIG 33) armed version, sometimes (mostly online) called SO-150, is also under question. There are only a few mentions (in different mostly online sources) of an M3A1/A3 being modified with such a weapon It was allegedly destroyed in its first combat mission. In addition, there is no information on its exact characteristics. It is unknown if the whole gun (with wheels or without them) was used, and there is no known pictures or document that exist to prove it. This modification was probably impractical, because it would have put a lot of stress on the tank’s chassis, especially when firing, but also because of the weight of the gun itself. Limited ammunition storage in this vehicle would also be a problem. The biggest drawback though would be the low-level protection for its crew, an important fact as this vehicle was supposed to be involved in close combat operations. If it ever existed, this vehicle could very likely have similar characteristics and problems as the similar German vehicle based on the Panzer I Ausf. B.

Conclusion

The Stuart was rated as a good vehicle compared to other captured enemy vehicles used by the Yugoslav Partisans. The positive side was the availability of a more than adequate number of spare parts (and there were enough numbers of Stuart tanks that could in case of necessity, be reused for spare parts) and ammunition. In contrast, captured tanks were available in smaller quantities or even only as individual examples, which complicated the maintenance and ammunition logistics. Availability of at least 59 Stuart tank offered great offensive punch, but in most occasions, Partisans used them in smaller groups and often supporting infantry in attack, reducing their offensive power. The 37 mm main gun was by 1944-1945 standards obsolete, and ineffective in its role as an anti-tank weapon. But as on the Yugoslav Front most enemy tanks were older types (such as the L6/40 and H35/39), it was not that much of a problem. But on several occasion, modern German tanks (and self-propelled vehicles) were almost immune to this gun, which forced Partisans to use the 6-pdr gun of the AEC armored cars. This was the main reason why the Partisans modified a number of damaged Stuarts and armed them with German captured weapons in an attempt to increase their firepower, proving they had the skill and imagination necessary to do such modifications effectively so that they could be used in combat. The Stuart proved to be very important to the Partisans and was involved in many hard-fought battles for the liberation of Yugoslavia.

A column of Stuart tanks preparing for an attack on Mostar in 1945. Source

Light Tank, M3A3 Specifications
Dimensions	Length 5.03 m, Width 2.52 m, Height 2.57 m,
Total weight, battle ready	14.7 t
Crew	4 (driver, driver’s assistant, gunner and commander)
Propulsion	Continental W-670
Speed	58 km/h, 32 km/h (cross-country)
Range	217 km
Armament	37 mm M6 gun, with three 7.62 mm machine guns
Armor	10-44.5 mm

Sources

The Stuart light tank series, Bryan Perrett, Osprey Publishing London.
Tanks of the world, George Forty, Hermes House,
Zbornik dokumenata i podataka o Narodnooslobodilačkom ratu naroda Jugoslavije, Beograd 1975.
Armored units and vehicles in Croatia during WW II, part I, Allied armored vehicles, Dinko Predoević, Digital Point Rijeka 2002,
Oklopne jedinice na Jugoslovenskom ratištu 1941-1945, Bojan B. Dumitrijević and Dragan Savić, Institut za savremenu istoriju, Beograd 2011.
Modernizacija i intervencija, Jugoslovenske oklopne jedinice 1945-2006, Institut za savremenu istoriju, Beograd 2010.
World War II Tanks and Fighting Vehicles, Leland Ness, HarperCollins Publishers 2002.
https://www.srpskioklop.paluba.info/m3/opis.htm
Magazine Arsenal No. 15, Aleksandar Radić, Beograd 2008,
Naoružanje drugog svetsko rata-USA, Duško Nešić, Beograd 2008.
https://www.znaci.net/arhiv/fotografije?slika_po_strani=50&fraza=&stranica=3
https://the.shadock.free.fr/Surviving_M3_M3A1_Stuarts.pdf

Sources

https://henk.fox3000.com/251.htm
https://sh.wikipedia.org/wiki/Prva_tenkovska_brigada_NOVJ
https://www.znaci.net/arhiv/fotografije?slika_po_strani=50&fraza=&stranica=76