germany lost the battle of the atlantic because
Battle of the Atlantic The Germans failed to stop the flow of strategic supplies to Britain. This failure resulted in the build-up of troops and supplies needed for the D-Day landings. The defeat of the U-boat was a necessary precursor for accumulation of Allied troops and supplies to ensure Germany's defeat.
Two-front war The most famous example of a two-front war was the European theatre during World War II, when Hitler's Nazi Germany had to confront the Western Allies on the west and the Soviet Union to the east. The Germans were unable to repel either of the advances on the two fronts and eventually lost the war. While there were other contributing factors, such as the insufficiency of the Wehrmacht for a long war and the abandonment of blitzkrieg tactics because of fuel shortages and a rising need to defend territory, the two-front war was an important factor in deciding when the German military would be forced to surrender.