By the spring of 1944, the countryside of
Great Britain had become a gigantic camp for allies, while serving as a supply depot. Over the previous year, the
Americans and
British had gained the upper hand over
Nazi U-Boats in the
Atlantic Ocean, and their planes had destroyed most of
Adolf Hitler's air force.
The Allies are now preparing for
Operation Overlord. Allied troops would cross the
English Channel and invade Nazi-occupied
France. This would force Hitler to fight a two-front war, since the Russian Allied force was keeping most of the German army busy in eastern Europe.
Operation Overload would require incredibly detailed planning, as well as perfect coordination and timing. General
Dwight D. Eisenhower was the
Supreme Commander of the
Allied Expeditionary Force (AEF). There was only a few days each month when the tides were right for the invasion, while storms moved out of the
North Sea and into the
English Channel. Decisions by Eisenhower had to precise with the Allies avoiding bad weather when possible.
Secrecy was also vital to the mission. Hitler's forces had built a wall of concrete bunkers and gun emplacements along the French coast, while they had tank traps, mines, and miles and miles of barbed wire.