Complex sentence: Prior to the German attack, the Soviets launched a counter-offensive; on 6 July, the 7th and 5th Mechanized Corps of the Soviet 20th Army attacked with about 1,500 tanks near Lepiel.
Split into simpler sentences: Prior to the German attack, the Soviets launched their counter-offensive. On 6 July, the Soviet 20th Army's 7th and 5th Mechanized Corps launched an attack with about 1,500 tanks near Lepiel.