Answer:
Hitler and his troops underestimated the power of the allied side making him realize that winning the war was far harder than he thought.
Step-by-step explanation:
During the battle of Bulge (the last major German attack), when Hitler was advancing towards Germany, American troops created small pockets to attack the German soldiers as they tried to come through. Surprisingly, Americans were able to win the battle to stop Hitler from taking over. Winston Churchill even claimed that it was the Greatest American battle of the war. This helped to pave the way towards victory for the allied side.