D-Day was the beginning of the end for not only the Germans but Hitler most of all. D-Day forced the Germans to fight a two front war again just as they had in WWI. Yet again the Germans could not handle war on both sides of them.
“By the end of June 1944, about a million Allied troops had reached France.” - "World War II." World Encyclopedia 2004.
Reinforcements for the infantry of D-Day had come in. On June 26th, 1944 the Allies captured the French port of Cherbourg. After that day, the Germans began to retreat. On August 25th, 1944 came the day that the French had been waiting for, Paris had been liberated.
On December 16, 1944
“the Battle of the Bulge, the last German offensive on the Western Front, begins. Hitler orders a quarter of a million troops across Luxembourg to push back the Allied forces.” - "Timeline: The War in Europe, After D-Day." NPR.
The German troops advanced 50 miles into Allied lines creating the “bulge.” However on Jan 16th, 1945 Germany was defeated in the Battle of the Bulge and Germany retreats because of Allied resistance and shortage of supplies. In March 1945 US troops cross the Rhine and Germany troops retreat more. One month later on the 30th of April, Adolph Hitler commits suicide. May 7th, 1945 World War II is officially over. Without the surprise invasion of Operation Overlord, the turning point in WWII would not have happened. Russia most likely would have fell and allowed Germans to over take the country. The world would be a different place.