Battle of Stalingrad Click to see full answer. Besides, what were the most important battles of World War 2? Major Battles Of World War II (WW2) Battle of the Bulge (December of 1944 to January of 1945) Battle of Berlin (April to May of 1945) Battle of Midway (June of 1942) Battle of Okinawa (April to June of 1945) Battle of Stalingrad (August of 1942 to February of 1943) Operation Barbarossa (June to December of 1941) Also, why was D Day the most important battle in WWII? The invasion of northern France in 1944 was the most significant victory of the Western Allies in the Second World War. The German Army suffered a catastrophe greater than that of Stalingrad, the defeat in North Africa or even the massive Soviet summer offensive of 1944. Furthermore, what was the first battle in ww2? Battle of Guadalcanal Who fought the hardest in ww2?Great Britain in my opinion was the hardest fighting military during world war 2.