Axis and Soviet air operations during Operation Barbarossa took place over a six-month period, 22 June – December, 1941. Aviation played a critical role in the fighting on the Eastern Front during this period, in the battles to gain and maintain air superiority or air supremacy, to offer close air support to armies on battlefield, interdicting enemy supply lines, while supplying friendly forces. The Axis air forces were generally better equipped, trained and experienced in executing military tactics and operations. This superiority increased because of the Great Purge in the 1930s and mass expansion of Soviet air forces, which did severe damage to organisational structures.