The A10 was also known as the Cruiser Mk II and was developed alonside the A9. The A10 was crewed by 5 men armed with a 2 pounder and introduced in December 1939. By 1941 the 2 pounder was proving ineffective against German armour and lacked the ability to fire High Explosive shells. A number of A10 were converted to A10 CS (Close Support) by fitting a 3.7" (94mm) howitzer in place of the 2 pounder which allowed an ammo load of smoke and high explosive shells.