D-Day's major effect on was to open a new front in the European war. This forced Germany to fight the Russians on one front and the Americans and British on the other. As with World War I, Germany was not able to fight a war on two fronts successfully.
The German army had faced setbacks on the eastern front against the Soviet Union. In addition to the psychological blow the invasion would have inflicted, the invasion meant that Hitler could not shift troops from France to help defeat the Soviets in the east.
D-Day occurred on June 6, 1944, in Normandy. The invasion began when paratroopers landed in France to secure roads and bridges. The amphibious invasion started at around 6:30 in the morning according to local time. By the end of that first day, around 156,000 allied troops had landed on Normandy's beaches. Some estimate that as many as 4,000 allied troops died in the invasion. By June 11, the Allies had secured the beaches, and 50,000 vehicles and 326,000 troops had landed.
The invasion force made quick progress after D-Day. The French port of Cherbourg was captured on June 26, and the Germans began to retreat. Paris was liberated soon after on August 25. By May 8, 1945, Nazi Germany had surrendered to the Allies.