The M3 Lee is the tank that it seems history has, if not forgotten, not been much interested in. Given its place in history, its descendant, the M4 Sherman, gets all the press. That’s a pity because without the M3 Lee, the M4 would not have been the tank it was…for better (mostly) or worse (yeah…that profile).
It’s not a new observation to state that the US was not at all prepared to fight WWII at the start of 1940. During the interwar years from the end of the Great War (subsequently termed WWI) and the start of WWII, the world’s economic state after the Great Depression meant that funding for another Continental war (or much else) wasn’t available. The state of America’s military had not advanced a great deal from WWI, particularly in armor. This state was not only technically but doctrinairely as well. Congress did not allocate funds to develop anything called “tanks.” The way military procurement worked around that was to term its armor as “combat cars.” Armored, tracked, and armed vehicles are not “cars,” they’re tanks, to my way of thinking but it’s obvious that Congress was clueless back then as well as today. The M1 and M2 series of tanks weren’t very good tanks, and they were very small tanks, but that’s what the US Army had so that’s what they worked with (as the war seemed more immanent, to train against medium tanks it was cheaper and easier to paint a big “M” on the side of the “combat cars” and treat them as if they were medium tanks).
Doctrine also affected the design of these tanks. Nobody was aware of the impending Blitzkrieg (nor was the US aware of Pervitin, which certainly added the “blitz” to the krieg) and the US did not see tanks as a separate tactical branch, subordinating armor to the infantry as it had been during WWI (and in fact had been developed for as evidenced by its trench-busting genesis). According to prevailing doctrine in the 30s, armor was to support infantry (a concept that reversed itself by the end of WWII when infantry supported tanks, particularly with the US Marines in the Pacific Theater).
Even in that role, US armor of the 30s was inadequate. Infantry tanks are best illustrated by Germany’s PzKpfw VI, the Tiger tank. It was heavily armored and mounted the largest gun (until the M26 Pershing, which used a 90mm gun of questionable effectiveness), and Britain’s Matilda. The Matilda’s armor was difficult for Panzer IIIs and short-barreled Panzer IVs to penetrate (everyone had problems with the Tiger’s 88) (even the Wehrmacht, but of a different sort).
Cruiser tanks were intended to operate independently of infantry as mechanized cavalry. Cavalry’s role was to exploit breaches of the enemy’s lines and raise havoc and mayhem behind the enemy’s lines, emphasizing speed and maneuverability over thick armor. Cruiser tanks weren’t expected to withstand incoming fire while moving at a walking (or running, if I’m the infantry) pace. They were less armored than infantry tanks, which allowed them to be faster and more maneuverable.
America didn’t have an infantry tank. (I haven’t seen any evidence that the US Army intended on having infantry tanks.) They had “combat cars,” and when it was decided that something larger than the M1/M2 series of “combat cars” and light tanks, respectively, was needed, Ordinance came up with the M2 Medium. It was armed by one 37mm anti-tank gun in a turret (which was a creditable anti-tank gun in the early to mid-30s and useless against armor by 1941) and machine guns every place they would fit. The M2 Medium also used the vertical volute suspension system and live tracks. What the M1/M2 combat cars/light tanks and M2 all had in common was an aircraft radial engine for motive power. The M1/M2 used a Continental R670 engine rated at 250 hp, the M2A1 Medium used a Continental R975 E2 engine rated at 400 hp. Using an engine originally designed for aircraft, the radial, resulted in a trait shared by both the M3 and M4 tanks. A high profile.
When WWII started, and particularly in the North African campaign, the first US tanks to be committed to action were M3 Stuart light tanks, armed with the 37mm anti-tank gun used in the M2 Medium. (By that time, as an anti-tank gun, the 37mm was useless…armor thickness had passed it by, unless the opponent was Japanese armor.)
The M4 medium tank was in planning stages and problems were encountered with producing a turret large enough for the 69” (175cm) turret ring that could handle the recoil of the new 75mm medium velocity gun. Rather than wait, because who knew how much time would be needed to solve those problems, it was decided to design a better M2 Medium using as many of its parts for the new tank as possible.
The M3 Lee was the result (once again, named by the Brits, probably because there were already enough different types of vehicles running around with an M3 nomenclature, because evidently no one was aware that there were many numbers that could be used, not just “3”). It used the same engine as the M2A1, the Continental R975, as well as the same suspension and track design. The most obvious difference was the 75mm main gun mounted in the right sponson (with limited traverse due to the mount). There was also a small turret on top with the obsolete 37mm gun as well as the Ordinance tradition of adding machine guns any place they would fit. There was a small cupola on top of the small turret with a .30 caliber (7.62mm) M1919A4 machine gun, another .30 caliber (7.62mm) coaxially mounted next to the 37mm, as well as two semi-fixed (adjustable in azimuth only…traverse was adjusted by turning the entire tank) .30 caliber (7.62mm) M1919A4 machine guns in a fixed mount in the bow to the left of the driver. The M3 Medium was a stopgap measure to get something in the field that could toss big enough rocks at the German tanks to discommode them (which it certainly did, leading to the PzKpfw IV being upgunned with a long-barreled, high velocity, 75mm gun). Having a turret on top of the already tall hull combined with its main gun being mounted in the right sponson meant that the M3 Lee couldn’t take advantage of hull-down defilade (fancy word for “hide behind a hill with just the gun poking over it”). Much of the tank was exposed when using terrain as a defensive barrier…meaning that the terrain didn’t provide much defense.
However, 6258 of these stopgap tanks were produced in several different variants. As useful as the M3 Lee, and the later M3 Grant with the larger 37mm turret used by the British, was, its real utility was as a test and development chassis for the impending M4 Medium tank.
With the exception of Ford’s GAA engine used in the M4A3 series of Shermans, every engine used in the Sherman had been installed in an M3 Medium first and bugs and problems were resolved there. Welded armor, which required a different type of steel than riveted armor, was first tested on the M3A2 Medium (12 produced). The M3A3 tested the GM 6-71 diesel engines (322 built). The M3A4 tested the Chrysler A57 Multibank engine (with a stretched hull to accommodate the longer engine, which was the same modification to the M4A4), as well as removing the side doors from the upper hull (109 built).
In addition to engine tests that were incorporated into the M4 Medium line, the M3 Medium was also the initial platform for the M7 (See? Other numbers than 3!) Priest (105mm howitzer Gun Motor Carriage) that saw widespread use (over 4000 encompassing three variants), M12 (155mm Gun Motor Carriage), M31 series of tank recovery vehicles (TRV), and the M33 (developed from the M31TRV with the turret and crane removed) as a Prime Mover tractor for artillery.
It seems that history has treated the M3 Medium more dismissively than it deserved. No, it certainly wasn’t a great tank with thin armor, a high profile, and a main gun with limited traverse due to its mounting in the sponson. But it was what Ordinance could get into the field quickly. It was mechanically reliable and served as one of the evolutionary steps (perhaps even the foundation) that led to the M4 Sherman tanks. At the time of its introduction to combat its 75mm gun was more than adequate (as well as for the first M4/M4A1 Sherman) against the Panzer III and IV.