expensive for infantry support, where they would be too vulnerable to anti-tank weapons and rejected claims that they could fire accurately when moving, so would gain no benefit from their speed. Martel preferred a large number of smaller and simpler tanks to swamp an opponent, instead of a few comparatively expensive medium tanks. Work should continue on a universal tank in the long term but from 1936 to 1939, Martel gave much thought to the infantry tank; he did not want medium tank development to be split but saw the logic of it, given the constraints on tank development. Tanks were necessary for mobile operations in armoured divisions and for infantry support in attacks on fortified defensive positions; a vehicle satisfactory for both tasks appeared to be impossible to attain. Two types of vehicle led to two theories and procedures, infantry tank thinking coming from the experience of tank operations from 1916 to 1918, when British tanks had been used for infantry support. Armoured division theory emphasised the speed of cruiser tanks and independent action to protect flanks, attack the opponent's flanks and rear, to counter-attack and conduct pursuit operations. Development Like naval cruisers, cruiser tanks were fast and mobile for operations independent from slower-moving infantry with their heavier infantry tanks and artillery. When gaps had been forced through the opponent's front by the infantry tanks, cruisers were to penetrate to the rear and attack lines of supply and communication centres in accordance with the theories of J.F.C. Fuller, Percy Hobart and Basil Liddell Hart. The cruiser tank was designed for use in a manner similar to cavalry, which made speed the most important factor and to achieve this, early cruisers were lightly armoured and armed to save weight. The emphasis on speed unbalanced the British designs; on limited engine power, the speed was possible only by sacrificing armour protection (by comparison infantry tanks operating at soldiers' pace could carry far more armour). The idea that "speed is armour" was considered most important in the Royal Tank Corps. It was not realised that the principle of mobility was a liability against the German policy of accepting lower speeds for superior armour and armament, ensuring that even one round from a German medium tank could easily destroy a cruiser. An even bigger problem for most cruiser tanks was the small calibre of their main gun. The first cruisers were armed with