September 1st, 1939. German battleship Schleswig-Holstein marks the start of World War II by firing on the garrison stationed at the Westerplatte peninsula in Poland.September 1st, 1939. German battleship Schleswig-Holstein marks the start of World War II by firing on the garrison stationed at the Westerplatte peninsula in Poland.September 1st, 1939. German battleship Schleswig-Holstein marks the start of World War II by firing on the garrison stationed at the Westerplatte peninsula in Poland.