After US entry into World War II and the formation of the Tank Destroyer Force, a suitable vehicle was needed to equip the new battalions.

By November 1941, the Army requested a vehicle with a gun in a fully rotating turret after other interim models were criticized for being too poorly designed.

After appropriate changes to the hull and turret were made, the modified version was selected for production in June 1942 as the "3-inch Gun Motor Carriage M10".

It combined thin but sloped armor with the M4's reliable drivetrain and a reasonably potent anti-tank gun mounted in an open-topped turret.

[4][5] U.S. combined arms doctrine on the eve of World War II held that tanks should be designed to fulfill the role of forcing a breakthrough into enemy rear areas.

The idea was to use speed and agility as a defense, rather than thick armor, to bring a powerful self-propelled gun into action against enemy tanks.

Using lessons learned from combat reports from the Philippines, the armor on the sides and rear of the upper hull was changed from flat to sloped plates.

By fall 1943, with its M5 and M9 competitors being eliminated from the design competition and their production contracts cancelled, the M10 was to become the United States' primary tank destroyer of the early war period.

The unique design of the hull hatches to clear the gun mantlet meant that the driver's view directly to the left side was obstructed.

Unlike the M4 tanks it was based upon, the M10 lacked an auxiliary generator, which forced the crew to run the main engines in order to recharge the vehicle's batteries.

The engine noise and smoke could attract enemy fire, especially in close quarters, where the M10 was vulnerable due to its thin armor and open-topped turret.

Soon after reaching production, it was realized that the barrel of the 3-inch gun M7 was too heavy,[11] to the point where it prevented traverse of the turret on a slope of more than four degrees.

As an attempt to improve the figure to fifteen degrees, the Army ordered that the track grousers and antiaircraft machine gun be stored on the rear of the turret.

This did not solve the balance problem, and on 21 December 1942, triangular "quick fix" turret counterweights made of lead, mild steel, or cast iron were authorized.

For combat use, the 3-inch Gun M7 could fire five types of ammunition: The M79 AP shot could penetrate 92 mm of homogeneous armor angled at 30 degrees from the vertical at 1,000 yards.

The M62 APCBC/HE-T shell was capable of penetrating 88 mm of homogeneous armor under the same conditions The T4 (later M93) HVAP shot was rare and was used in small numbers beginning in September 1944.

This shot featured a sub-caliber tungsten carbide penetrator encased within a steel jacket and aluminum body and ballistic "windshield".

[16] The M42A1 high explosive shell was used for indirect artillery fire or against fortifications and soft targets like infantry in trenches or antitank guns.

A .50 caliber (12.7 mm) Browning M2HB heavy machine gun could be mounted on the top rear of the turret for use against enemy infantry and for anti-aircraft use.

[citation needed] The M10's heavy chassis did not conform to the quickly evolving tank destroyer doctrine of employing very light high-speed vehicles, and starting in the summer of 1944 it began to be supplemented by the fast M18 Hellcat.

In reality, this was not the case and M10 battalions were attached, often semi-permanently, to infantry and armored divisions to provide additional direct and indirect fire support.

Typical missions included providing indirect artillery fire by augmenting divisional artillery units, following and supporting the lead elements of an infantry assault, attacking obstacles such as fortifications and enemy vehicles (including tanks) that hampered the advance of friendly units, and setting up an antitank defense once the objective was secured.

[19][20] By October 1944, the improved 90 mm Gun Motor Carriage M36 began to arrive in Europe, and mostly replaced the M10 by the end of the war.

The plans to retain any towed battalions at all were canceled after their generally poor performance and high losses in 1944, especially during the Battle of the Bulge.

The M10 proved unpopular in the Pacific due to its open turret, which left it vulnerable to Japanese close-assault antitank tactics.

Although the 17-pounder was a similar bore to the 3-inch gun M7, it had a longer barrel and used a larger propellant charge giving far superior armor penetrating capabilities.

This unit served on the 3rd Belorussian Front in 1944, taking part in summer campaigns in Belorussia, the Baltic, and East Prussia.

After building the prototype, France taught Israel how to do it themselves and provided their technical knowledge related to this development along with a contract to sell the SA50 guns and ammunition.

The 893rd Tank Destroyer Battalion took many casualties from artillery fire and tree bursts and lost 16 of 24 M10s during the Battle of the Hürtgen Forest.

[29] The crew was also exposed to sniper fire and infantry close assault, such as grenades thrown through the open turret, or attacks from upper story-windows, especially in urban warfare and wooded areas.