The Battleship That Started the War
On September 1st, 1939, this happened (via Wikipedia):
At the end of August 1939, Schleswig-Holstein sailed to Danzig, under the pretext of a courtesy visit, and anchored in the channel near Westerplatte. On 1 September 1939, at 4.45 a.m. she began to fire 280mm and 170mm shells at the Polish garrison there. The Battle of Westerplatte lasted seven days. After the capitulation of Westerplatte, the Schleswig-Holstein battered Gdynia, Kepa Oksywska, and the Hel Peninsula. During the bombardment of the last she was hit by a 152 mm shell from the Polish battery.
Fortunately, the war ended on a different Battleship, 6 long years later: