Tank doctrine in the UK declared that one group of tanks would accompany infantry in a similar role to World War I, while another group of 'cruiser' tanks would then exploit a breakthrough, in a role similar to light cavalry. In the USSR, 1930s tank doctrine specified three groups of tanks: one 'breakthrough' tank in the infantry support role, one tactical breakthrough tank to clear the combat area, and a 'fast tank' for operational maneuver. In Germany, the ideas of Heinz Guderian established the need for unified tank formations, but with a mixture of armaments for differing roles.