Gdansk, Poland ? On a wind-swept peninsula where shells lobbed from a German battleship ignited World War II 70 years ago, European leaders vowed Tuesday never to forget the lessons of the 20th century’s bloodiest conflict.

Evidence of continued animosity was not far from the surface, however, as Poland pushed for greater acknowledgment from Russia of its role in starting the war, while Russia sought to minimize the impact of Moscow’s 1939 pact with Berlin.

At dawn on Gdansk’s Westerplatte peninsula, Poland’s leaders marked the hour the German battleship Schleswig-Holstein shelled a tiny Polish military outpost housing the navy’s arsenal. It was the war’s opening salvo.

Red and white Polish flags fluttered in a breeze as the officials opened the ceremony at 4:45 a.m. Later, Poland’s president, prime minister and others placed wreaths at the foot of the towering granite monument to the defenders of Westerplatte as an honor guard looked on.