On the eve of war in 1941, the Soviet armed forces were the largest in the world, and they consisted of two main branches: the Army and the Navy. The Red Army was of finally known at the time as the Red Army of Workers and Peasants (RKKA: Rabochiy Krestyanskaya Krasnaya Armiya). Under the Army were the Ground Forces, Air Force, National Air Defence Force and Armed Forces Support. The Ground Forces were the largest single element, making up 79.3 per cent of the armed forces, while the Air Force was 11.5 per cent and the Navy only 5.8 per cent. The primary focus of this book is the Ground Forces. By the start of 1939 the Red Army consisted of 84 rifle divisions, 14 mountain rifle divisions, 5 rifle brigades, about 25 cavalry divisions, 4 tank corps, 24 separate light tank brigades and 4 heavy tank brigades. With war evidently approaching the Army began activating new rifle divisions in August 1939 and on 17 September reservists were mobilized. Following the conclusion of the campaign in Poland in September 1939 in October the tank corps were abolished and further rifle divisions activated.