person as they saw fit. An M1903 Springfield rifle with 60 rounds of ammunition was stowed next to the assistant driver, and an adapter for the rifle and ten M9 rifle grenades for use against tanks were stowed under the left front vehicle subfloor. Storage boxes in the turret held five Mk 2 grenade, five M18 smoke grenade, and two thermite grenades. Combat use United States Army 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. American tank destroyer doctrine called for tank destroyers to be kept in reserve and rushed forward to counter massed enemy armored attacks. 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. The combat debut of the M10 came on 23 March 1943, during the Battle of El Guettar, in the Tunisian campaign part of the larger North African campaign. The M10 was initially successful as its M7 3-inch gun could destroy most German tanks then in service. During the battle, M10s of the 899th Tank Destroyer Battalion and M3 Gun Motor Carriages of the 601st Tank Destroyer Battalion destroyed 30 German tanks, although 20 M3s and 7 M10s were lost. The M10 did not see much anti-tank action for the rest of the North African campaign, and instead was used as mobile fire support. During tank fighting in the Normandy campaign, the M10's 3-inch gun was proven to be ineffective against the thick frontal armor of the German Panther medium tank. On 6 July 1944, Eisenhower's headquarters requested that all M10 battalions be converted to the new M36 as soon as possible. On 10 July 1944, the 899th Tank Destroyer Battalion blunted a German counterattack by the Panzer Lehr Division near Le Dézert and destroyed 12 Panther, one Panzer IV, and one Sturmgeschütz III assault gun in a fierce two-day battle, most of it taking place at ranges