Leaders mark 70th anniversary of World War II

Germany's pre-dawn invasion began when the battleship Schleswig-Holstein fired on the Westerplatte military base in Gdansk harbor on September 1, 1939.

The attack set off a chain of events that eventually embroiled all of the world's major powers in the war. The conflict lasted until September 2, 1945 when Germany's ally Japan signed an unconditional surrender.

Leaders from many of those nations were in Gansk on Tuesday for a wreath-laying ceremony at the Cemetery of Defenders at Westerplatte, with commemoration speeches to take place in front of the Westerplatte memorial.

Among those attending were German Chancellor Angela Merkel and Russian Prime Minister Vladimir Putin -- leaders of the two nations that once held power over Poland.

Merkel said on Tuesday that her country unleashed "endless suffering" by starting the war, but also recalled the fate of ethnic Germans expelled at the end of the conflict.