In British practice, the main armament of the infantry tank went in three phases. The pre-Dunkirk British Army Matilda I had only a single heavy Vickers machine gun, a compromise forced by the lightness of its chassis and its target cost. The Matilda II gained a capable anti-tank capacity for its time, with the 2-pounder, but these were only issued with solid-shot (i.e. non-explosive) for anti-tank use and had little effect as artillery when providing close support for the infantry. A separate variant of the Matilda was fitted with a 3-inch howitzer. The ultimate evolution of the British infantry tank concept began with the Churchill Mk I, where a hull-mounted 3-inch howitzer could support infantry assaults with HE shells while the turret had a 2-pounder for use against other tanks. As the increasing size of tanks, and their turret ring diameters, allowed such a howitzer to be turret-mounted in vehicles such as the Crusader Close Support (CS) and Centaur CS cruiser tanks.