Operation Overlord, the code name for all the plans formulated and carried out by General Dwight D. Eisenhower involved in the final defeat of Germany, began on June 6, 1944. They had it planned for a while, but had to wait for acceptable weather conditions. No one knew why the attack was called D-Day. The Allied powers (mainly US, France, and United Kingdom) had an attack planned on Normandy Beach in France, while Germany (our main enemy) thought it was going to be somewhere else. Germany was part of the Axis powers (mainly Germany, Italy, and Japan), and were caught off guard by the attack.