Germany invaded Poland on September 1 after having signed a non-aggression pact with the Soviet Union in late August. The German attack began in Danzig, with a bombardment of Polish positions at Westerplatte by the German battleship Schleswig-Holstein, and the landing of German infantry on the peninsula. Outnumbered Polish defenders at Westerplatte resisted for seven days before running out of ammunition. Meanwhile, after a fierce day-long fight (1 September 1939), defenders of the Polish Post office were tried and executed then buried on the spot in the Danzig quarter of Zaspa in October 1939. In 1998 a German court overturned their conviction and sentence. The city was officially annexed by Nazi Germany and incorporated into the Reichsgau Danzig-West Prussia.