Sirens wailed and religious leaders led prayers for the dead as the presidents of Poland and Germany stood together solemnly Thursday on the Baltic peninsula where World War II began 66 years ago. Horst Koehler is only the second German president to attend the annual ceremonies on the Westerplatte peninsula, following the example of his predecessor, Johannes Rau. His presence comes amid signs of deepening friendship between the former foes, despite some lingering bitterness.

In 1939, Poland was invaded by Germany to its west and the Soviet Union to its east. After the Nazis attacked the Soviets, Poland came entirely under German control and subject to a brutal occupation. It become the hub of Hitler's program to exterminate Europe's Jews, under which 6 million were murdered.

At the ceremony on Westerplatte, Koehler and Polish president Aleksander Kwasniewski walked to a monument to the war's first victims. They were killed on the peninsula in the Baltic port of Gdansk when a German warship began shelling a Polish munitions depot and garrison on Sept. 1, 1939, as the Nazis launched their invasion.

To the roll of military drums, Koehler and Kwasniewski walked behind soldiers, who placed large wreaths on their behalf, and bent over simultaneously to arrange the wreath's ribbons, each in the colors of their respective national flags.

The presidents then took two steps back, joined hands for a moment of silence and bowed toward the wreaths.

At a Gdansk high school later, the two stressed the need for tolerance between cultures, especially in fighting terrorism.