Russia entered the war when Nazi Germany carried out Operation Barbarossa. They missed the start date by 3 months and this would have led to one of the many problems that Nazi Germany faced during the war on the Eastern Front. Russia delivered Germany's greatest defeats, including the Battle of Stalingrad and the Battle of Kursk. Without these two battles Germany would not have had the significant losses of personnel and supplies that it faced in the last 3 years of the war. The Battle of Stalingrad is believed to be one of the most significant strategic battles for the Germans. If Germany had won Stalingrad, the Russians would not have been able to fight. Instead, Germany hastily decided to attack to prevent Russia from devising a strategy that would put Germany at a disadvantage. At the end of Stalingrad the Russians managed to push the Germans back and put them on the defensive. If Russia had lost in the battle against Nazi Germany, the United States and Great Britain would have faced a much tougher fight against Nazi Germany. Some even argue that it would have been nearly impossible for America to win against the Nazis