The lengths.

On February 5, 1945, with World War II in its last desperate months, a German train made its way to the city of Linz. Suddenly, Allied planes swooped in, dropping bombs and derailing it. As the train’s cargo—mail bound for several northern Austrian towns—scattered over the area, a second wave of bombers flew in with a strange payload.

Eight mail bags hit the ground around the train with a thud. Inside each bag were 800 propaganda letters, all addressed to homes and businesses along the train’s route and appropriately stamped. When the train was discovered, German postal workers recovered the bags and delivered the letters without being any wiser about their contents or origins.

Operation Cornflakes had begun.

http://www.businessinsider.com/operation-cornflakes-how-the-allies-got-the-nazi-postal-service-to-deliver-their-propoganda-for-them-2012-3