During world war two the battle that turned the tide of war against germany on the eastern front was the

 The Battle of Stalingrad

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Germany had invaded the Soviet Union in what they called Operation Barbarossa, beginning in June, 1941.  The Battle of Stalingrad, fought from August 1942 to February 1943, became the turning point in the war between German and Soviet forces on the Eastern front of World War II.  Stalingrad was a protracted and extremely bloody military confrontation.  More than 2 million troops were involves, and the death toll (including many thousands of Russian civilians) also numbered around two million.  As reported by the History Channel, "The Battle of Stalingrad (one of Russia’s important industrial cities) ultimately turned the tide of World War II in favor of the Allied forces."

when world war i broke out across europe in 1914, president woodrow wilson proclaimed the united states would remain neutral, and many americans supported this policy of nonintervention. however, public opinion about neutrality started to change after the sinking of the british ocean liner lusitania by a german u-boat in 1915; almost 2,000 people perished, including 128 americans. along with news of the zimmerman telegram threatening an alliance between germany and mexico, wilson asked congress for a declaration of war against germany. the u.s. officially entered the conflict on april 6, 1917.