What strategy did the allies use to defeat the germans in world war 2

The answer to this question is that the allies squeezed the Germans from two directions. 
Faced by battle from two fronts, Germany had to divide its soldiers. The Brits and the Americans launched series of air strikes across Germany towns, and also attacked from North Africa under,Eisenhower. tThis was a crucial battle because, it led to victory into Italy through Sicily which divided the focus of Hitler's forces. The Russian had also turned the tables in the battle of Stalingrad and were fast advancing against the Germans.