On August 25, 1939, the aging German pre-dreadnought battleship Schleswig-Holstein arrived in the port of the Free City of Danzig. Officially, it was there to celebrate the anniversary of the German victory in the Battle of Tannenberg in World War I: colorful flags flew from the masts and the men stood at attention in their white dress uniforms, brass buttons shining in the late summer sun. But the ship had a more sinister purpose. Unbeknownst to onlookers, over 200 marines were hidden below deck, preparing for a deliberate and unprovoked attack against Poland. In the gray morning light of September 1, 1939, the ship quietly moved the short distance from Danzig harbor to the Bend of Five Whistles, across from the small Polish military transit depot at Westerplatte.