As we commemorate the 75th anniversary of D-Day, it's important to recall that the invasion of Normandy on June 6, 1944 was no "sure thing." In addition to years of operational planning, the Anglo-American forces had to win the Battle of the Atlantic against German U-boats, secure the air space over the channel and into northwestern France, and land the largest amphibious force in the history of the world. In order to gain essential time, the Allies had to achieve tactical surprise for the initial invasion. This inspired "Operation Bodyguard," the ambitious deception campaign that sought to convince Hitler and his staff that the invasion was intended at another place and time. Its success provided the Allies with the margin of error required for victory. We will use this important event to examine the politics, diplomacy and strategy of D-Day, as well as the tactical plans, logistics and intelligence work that helped it succeed.