Origins: The M3 Stuart
The US Army needed a more convincing light tank than the small M2, especially after the 1940 campaign, following a new tactical thinking about armored forces in the USA. A light, fast tank, equipped with one of the most common guns for its category, a 37 mm (1.46 in), was designed, bearing, initially, an impressive batch of five cal.30 (7.62 mm) M1919 Browning machine guns, which were lately reduced to three (one of the turret roof, one coaxial in the turret, and one in the hull).
The initial production run of the M3 was of 5811 vehicles, most of them being used by the British and redesignated Stuart Mk.I and Mk.II. Then, the M3A1, or Stuart Mk.III and Mk.IV (diesel) in British service, appeared and were massively used in Africa (Operation Torch), then Tunisia and Sicily. In 1942 came the M3A3, which was influenced by the M5 design. In all, 13,859 M3 were built and fought in almost all theaters of war. In Europe, they faced much better German tanks, and their feeble armament and armor, their radial gasoline engine, were seen as handicaps. This was not the case in the Pacific, where they were still a match for the smaller Japanese tanks.
Genesis & development of the M5
The core reason behind the development of the M5 was probably the rapidly growing demand for radial engines, which were in short supply. Therefore, other sources were approached in order to have the tank production still running in early 1941. In June, OCM 16837 authorized the installation of two Cadillac engines mated on a single crankshaft and hydramatic transmission and auxiliary transmission M3 (transfer case). Cadillac had been, indeed, rarely involved with wartime production until then. The combination of systems gave 6 speeds forward and one reverse, and a very smooth steering. The M3E2 prototype was therefore tested with this arrangement on a 2000 miles (3200 km) crash course at the GM proving grounds. The results being excellent, testing resumed at Aberdeen, aiming to gain the General Staff’s approval. Although this modification made the M3 2,500 lbs heavier (1133 kg), performance was overall preserved. The vehicle required a lower temperature starter, was quieter and more compact, freeing space inside because of the lower drive shaft. It also benefited from both simplified maintenance and training.
By November 13, 1941, the new tank, designated M4, was tested with this engine and transmission, while the M3A1E1 prototype tested a new hull construction, largely welded. A decision had both projects combined to give the M3E2, then the M3E3. Among other modifications, the sloped front glacis was moved forward to free more space inside, and the two rotatable hatches with periscopes were fitted on the flat section following the glacis, for the driver and the bow gunner. All the tooling exterior stowage was relocated on the flat and sloped rear section of the back plate. There were a crowbar, handbar, shovel, hammer, pickaxe, axe, pincer, and two double links that were fitted on the two corners of the back plate. The most obvious difference between the M3A3 and the M5 was the shape of the rear hull, much roomier. In the end, to avoid confusion with the M4 Sherman, the name was changed to “M5” in February, when the production was approved and started at the Cadillac division of the GMC plant in Detroit, on 30 April 1942. The run ended in December the same year (1470 built), when an improved model succeeded it, the M5A1. Others were built, starting in August, at the Southgate California plant (354 tanks) and Massey Harris Company (250). These were mostly exported. The grand total was 2075 tanks.
Design specifics of the M5
The turret, main hull, tracks, suspension system, almost everything including equipment, were derived from the M3A3, so the production lines needed only a few changes. The new engine and transmission arrangement saw the rear part reshaped and steel RHA was used, along with welding, throughout construction. A .30 cal (7.62 mm) machine-gun was placed on the right side of the glacis and was operated by the assistant driver, who sat on the right. Both his and the driver’s seats could be elevated in order to be able to ride with their heads out of the hatch. The assistant driver and driver were given dual steering brake controls, and floor mounted accelerator pedals.
The M3A1 turret was adopted for the M5, the “short” model characterized by the roof machine gun placed at the rear. The gunner needed to stand behind, exposed to enemy fire. This was corrected with the M5A1. The turret had a Westinghouse gyrostabilizer and oil-gear power traverse. Thanks to the new powerplant and lower drive shaft, the turret traverse systems could be mounted under the turret floor, freeing space in the process. The turret was equipped with an M23 gun mount and roof mounted M4 periscopic sight for the gunner, under an armored cover. It was originally meant to have a telescope left of the gun. The port for it was welded shut.
Despite criticism about its lack of firepower, the 37 mm (1.46 in) was kept. Its high-velocity performances made it able to pierce the armor of similar light tanks. As a scout tank, it was mostly confronted with infantry, and the three Browning machine-guns were also an argument.
In all, 2075 M5s were produced (including the British versions) and the first M5s to see combat action were part of the November assault in North Africa (operation Torch). Until then, all the M5 produced were intensively used for training in relevant locations, like the Indio desert training camp in California.
Regarding reliability and maintenance issues, the dual Cadillac engine and hydramatic transmission were questioned by the Ordnance bureau, especially when looking at standardization issues. The arrangement looked complicated and perhaps not sturdy enough to be suited for intensive use in combat conditions. The other problem was related to this second type of tank (the M3A3 was still produced alongside), which complicated maintenance and driver training. But all these doubts were lifted when intensive trials (including a 3370 miles/5400 km run without incident) done by the Armored Forces Board reported that this tank attained an unprecedented level or reliability and was superior in performance and efficiency to any previous US tank type in service. More so, when the M5 entered service, American drivers were unexpectedly happy to drive a “Cadillac” in wartime. Last but not least, the automobile-grade, lower octane gasoline made the M5 much safer in operations when hit. The British too were quite happy with the new light tanks (also dubbed “Honey”), as they were even easier to drive and quieter.
This was the second production version of the M5, which can be distinguished by the extended M3A3 turret model. The turret itself helps to distinguish between the early and later models, as on the early models, there were still pistol ports in the side walls. The extra bustle provided room for the more powerful SCR 508 radio and antenna mounted at the extreme rear. To avoid interference with it, the cal.30 (7.62 mm) pintle mount had to be shifted from the back plate to the right hand side turret wall. Because of this, it could only be fired by one of the crew -often the commander- from inside the turret, a considerable advantage for protection. But the cal.30 (7.62 mm) had been woefully criticized in action as being totally inefficient against the fast-flying aircraft of 1942-43. On the M24 Chaffee, only a cal.50 (12.7 mm) was retained. However, this mount received some shielding on later production version. There was a removable plate on the rear wall of the bustle, for easy extraction of the M6 37 mm (1.46 in) rounds. The side pistol ports were first redesigned, then eliminated, and earlier models had theirs removed and the opening welded shut. Also, particular to the M5A1 was the escape hatch added under the assistant driver’s seat. The hull and turret in general received better watertight sealing.
Another characteristic feature was the addition of large protective sand skirts over the upper tracks, which were used by some early models in their integral form (two mudguards, upper side skirt, lower side skirt fastened to the bogie legs hooks). In practice, the latter was dropped most of the time, and many M5A1s were seen lacking the rear mudguard, more rarely the front one, or often the whole kit was dismounted as it clogged and could be torn out. Other points were the massive stowage basket at the rear, roof spotlight, improved cal.30 (7.62 mm) mount and shield around the mount. Turret rails were welded for strapping spare track links, in two groups of four up and down. On the late series, the “rails” were continuous, allowing to strap a full side wall length of spare track links. Also, the original spoked roadwheels were replaced by a simpler cast, filled ones and the cal.30 (7.62 mm) mount was modified.
Production and late modifications
On 24 September 1942, the new tank, standardized as the M5A1, was designated to replace the M5 at the Cadillac plant in Detroit. Production only started in November (1196 tanks), December for the Southgate plant (Calif.), and Massey Harris (3530). In the meantime, the American Cars & Foundry was brought into the program in October 1943, producing 1000 more. In all, 6810 M5A1s were delivered, the last by Massey Harris in June 1944. Three time more M5A1s were built compared to the M5. However, American Cars & Foundry remanufactured early M5A1s to incorporate the late version features, like the rear stowage basket, between November 1944 and June 1945.
Due to the weight increase of the M5A1, which rose to 17 tons, the standard issue 11 1/8 in tracks were no longer capable of easing ground pressure on muddy and snowy terrains in a satisfactory way, and, in order to improve this, three prototypes, the M5A1E1, were ordered by the Ordnance committee in March 1943. Modifications at the Cadillac Plant included 3 1/2 inches spacers welded to each side of the hull, on which the standard suspensions brackets were installed. Thanks to these operations, a 16 1/2 in wide single pin track (T65) was developed by Burgess-Norton, which basically had the same system fitted as on the late HVSS Shermans “Duckbill” track extensions. Trials failed and two other 18 inches tracks (T75) with double pins or simply widened links were tried at Aberdeen, without much success. The whole experiment was canceled in 1944. There were also attempts to replace the M44 mount and the T73 model was tried with the M6 gun, without much success, and terminated in July 1944.
An M5A1 preserved at Worthington Tank Museum. It is showing its left side deflector, a common feature on the late M5s.
M8 Scott SPH
The most famous derivative was the HMC M8 Scott, HMC standing for Howitzer Motor Carriage. It was basically an M5 with a new turret equipped with a regular ordinance 75 mm (2.95 in) M2 howitzer, and a heavy cal.50 (12.7 mm) machine gun for immediate defense. 1778 of them were built, including the M8A1 variant based on the M5A1 chassis.
Other SPGs: T18, T82
Other self-propelled artillery variants included the T18 of 1943 (with a 75 mm/2.95 in M1A1 in a boxy superstructure) and the T82 equipped with an 105 mm (4.13 in) howitzer in 1945.
Mortar Carriers T27/29 & T81
The T27/T27E1 were prototypes developed on a turretless M5A1 chassis. The T29 was a paper project, whereas the T81 was a chemical mortar carrier, carrying a 107 mm (4.22 in) heavy mortar. It was tested but never produced.
AA Carriages T65 & T85
The T65 was modified for anti-aircraft defense, equipped with a twin 40 mm (1.57 in) Bofors mounted on an M5A1 chassis. The general design was later adapted for the M24 chassis and became the well-produced M19 GMC. The T85 had a 20 mm (0.79 in) Oerlikon in a quad mount. It was tested but abandoned after trials.
Command version M5 COM
The only other large-scale variant was the command version, without a turret, but a small superstructure instead, equipped with a single cal.50 (12.7 mm) machine-gun and powerful radio equipment.
Recce version T8
On 21 December 1943, the Army Ground Forces requested an armored recce tracked vehicle. On 17 February 1944, the Ordnance department ordered two M5A1s to be modified to test an open fighting compartment version. The T8 was a turretless version, fitted with a 12.7 mm (0.5 in) Browning M1920A4 heavy MG on a ring mount, protected by a bathtub like shield. The T8 had its machine gun fitted on the right-rear of the fighting compartment, whereas the T8E1 saw its cal.50 nearer the turret ring. The latter also used new 16 in (40 cm) metal tracks. In addition, both vehicles could carry ten antitank mines on the outside of the right sponson. Both were tested at Fort Knox, the T8E1 being judged superior and retained for production. However, the Armored Force Board wanted to use the M24 light tank chassis instead for the intended role, and only a limited numbers of T8s were accepted as “limited standard” service vehicle, used in Europe in 1944-45.
Flame-thrower version Zippo
There were three variants that only differed by a few specs: The E5R1, E7-7 and ER9-9 based on the M5A1 chassis. Of all three prototypes, the main gun was replaced by the flame gun, and a flammable liquid reservoir was installed inside the hull. These vehicles were intended for the Pacific campaign.
Some M5A1s were equipped with an E5R1-M3 or E7-7 mounted in the hull, replacing the forward cal.30 (7.62 mm), and others had a dozer blade (M5 Dozer), having the turret removed, working as engineering vehicles in the Pacific theater of war. The T39 MRL was a proposed conversion project intended for infantry support in the Pacific, a regular M5 version rearmed with a T39 20 rocket launching kit.
Foreign users and postwar career
Many Chinese, French, Portuguese versions, which were in service during the fifties and sixties, incorporated a few custom modifications. No less than 33 countries had M3/M5 Stuarts in their arsenals (mostly in South America), some until the beginning of the nineties. The French M5A1s participated in the Indo-Chinese campaign until 1954, and the Portuguese ones (only three) served in Angola in 1967.
The M5 & M5A1 in action
Both light tanks quickly replaced the earlier M3s still in service and rapidly gained a reputation for themselves. The M5 was reclassified as limited standard when the M5A1 became available, and the latter was reclassified substitute standard when the M24 Chaffee became available, but served until the end of the war. Many surplus tanks found a long postwar career under other flags. Aside from the 1131 British Stuart Mark VIs, only five reached the Soviet Union (fate unknown). 223 were given to the poorly equipped French Army in North Africa, which later were integrated into the 1st Free French Army and served in Italy, France and Southwestern Germany. The American M5/M5A1s were battle-tested in Tunisia, Sicily, Italy, France (Normandy and Provence campaigns in the summer of 1944), and Germany, but also the Pacific, in growing numbers after they were discarded in Europe by the arrival of the Chaffee. Many were modified for special duties, like the “Zippo” flame-thrower variant, among others.
The Stuart Mk.VI (British service)
There were no name differences between the M5 and M5A1 in British service, as they were both called Stuart Mk.VI. No modifications were applied to the base model. Under Lend-Lease, 1131 M5A1s total were allocated to Great Britain. The British Stuart VI saw extensive service in the last stages of the desert campaign (fall 1942, 2nd El Alamein battle, Tunisian campaign). They joined the invasion force during Operation Husky (Sicily) and Italy thereafter. Some M5 Stuart Recce armored transports and command Stuart Kangaroos were also seen in action under the British flag. Long before the American forces, the British ceased to use them otherwise than in flanking units. The First Division of the US army painfully learned this at Kasserine pass. These tanks remained on the first line until the very end of the war in the Pacific.
Succession: The M24 Chaffee
Despite the fact the M7 was originally scheduled to replace the M5/M3 in 1943-44, a brand new light-medium model was ordered to replace it, the M24 Chaffee. The M7 was too mediocre to be a true medium tank, and too heavy to be suitable as a proper replacement for the previous M3/M5. The Ordinance Bureau quickly planned a new model from scratch, only retaining the M5 powertrain, with the objective of weighing under 20 tons in battle order. It was attained with a relatively thin but well sloped armor, and a new lightweight 75 mm (2.95 in) gun, which was borrowed from the B25 Mitchell “gunship” variants, in a three man turret. This answered, at last, to the oldest critic about the previous series, the weakness of their main armament. After successful trials in October 1943, production began in early 1944, and, when it stopped in August 1945, 4731 M24s had been built. They were very successful light tanks, fast and well-armed, largely exported and involved in many postwar conflicts.
Links & resources the M5 Stuart
The M3/M5 history on Wikipedia
Stuart: A History of the American Light Tank, vol.I, by R. Hunnicut
M5A1 Stuart specifications
|Dimensions (L-W-H)||4.62 x 2.39 x 2.33 m
(15’2″ x 7’10” x 7’8″)
|Total weight, battle ready||16.5 tons (33,070 lbs)|
|Crew||4 (commander, driver, gunner, loader)|
|Propulsion||Twin Cadillac V8, 296 hp (220 kW), air cooled gasoline|
|Suspension||Vertical Volute Spring|
|Speed||36 mph (58 km/h) on-road
18 mph (29 km/h) off-road
|Range||160 km (99 mi) at medium speed|
|Armament||37 mm (1.46 in) M6 AT gun
3xcal.30 (7.62 mm) M1919 machine-guns
|Armor||From 13 to 51 mm (0.51-2 in)|
|Production (M5/M5A1 combined)||8,884|
M5 Stuart, Tunisia, February 1943. Following operation “Torch” in November 1942, the first M5 arrived in North Africa.
Stuart Mark VI Kangaroo, Operation Torch, North Africa, November 1943.
Early Stuart M5 of the 81st Reconnaissance Batallion, 1st Armoured Division, Maontaione, Italy, July 1944.
M5A1 Annie B., Normandy, summer 1944. This tank proudly shows the emblem of the 66th Armoured Regiment, the oldest armoured unit in the history of the United States, founded by then Col. Patton of the US cavalry, which later commanded the 304th Tank Brigade during the late part of the campaign in Normandy and France.
Stuart M5A1 of the 757st Tank Batallion, Mount Porchia Italy, January 1944.
M5A1 with partial skirts and extra rear basket, 1944.
M5A1 “Lil’ Red Hen”, France, fall 1944.
M5A1 Stuart “Dingbat” of the 6th Armoured Division, 15th Tank Batallion, D Company, Western Germany, February 1945.
M5A1 “Buddies”, 3th Armoured Division, Western Germany, early 1945.
British Stuart Mk.VI seen from the left, to show the turret cal.30 mount shield, which was customary on most late M5A1s. Now exposed at the Bovington tanks museum.
M5A1 early production, 4th Marine Tank Batallion of the US Marine Corps on Roi-Namur, Kwajalein Atoll, February 1944.
British Stuart Mk.VI in the Netherlands, Operation Market Garden, fall 1944.
Taiwanese M5A1 in 1949.
Portuguese M5A1 in Angola, 1967.
Thanks to the determination and enthusiasm of Cavalry Captain Paulo Mendes, three rusty, obsolete M5A1 tanks were the protagonists of a unique adventure on the African soil, the only ones to have fought in the history of the Portuguese Army. These veterans successively served with the British, French (with Leclerc’s 2nd DB which liberated Paris) and the Canadian Army postwar, until 1956. The next year they were completely revised, refurbished and re-engineered, tested and approved for service at the Beirolas material tank depot. Named Gina, the Milocas and Licas, the 3 tanks embarked for Angola in 1967, and soldiered there until 1972, distinguishing themselves in many escort and reconnaissance missions, and being dubbed by the guerrillas of the FNLA “dumdum Elephants”. In 1967, 90 M5A1s were in still service with the Portuguese Army, the 6th Cavalry Regiment, the Military Academy, the National Guard (25 combined) and the General Depot of Beirolas. Captain Paul Mendes, accompanied by a driver and a mechanic, went in Beirolas for a week and selected six M5s which passed through an initial review, and only three were selected and taken to the General Workshops Engineering Material (OGME) in Bethlehem for a complete revision, equipped with new radios, ammunition supplies and prepared for shipping in September 26, 1967. The Milocas operated in Grafanil, the Gina in Luanda and the Licas in Zala. Only 13 are preserved today in Portugal.
M24 Chaffee, which replaced the Stuart, 1944. (off scale)