WESTERPLATTE, Poland — President Vladimir V. Putin of Russia was not invited. President Trump abruptly canceled. And as other global leaders gathered in Poland on Sunday to commemorate the start of the deadliest conflict in human history, the event served to underscore the divisions in Europe and within Poland itself.

In Warsaw, President Andrzej Duda of Poland used the occasion to chide other European leaders for not taking the threat posed by Russian aggression seriously, making an analogy to the policies of appeasement that allowed the Nazi party to rise in Germany.

“We are still faced, even in Europe, with the return of imperialist tendencies, attempts to change borders by force, assaults on other states, taking their land, enslaving citizens,” he said at a ceremony in Pilsudski Square.

“Closing one’s eyes is not a recipe for peace,” Mr. Duda said. “It is a simple way to embolden aggressive personalities. It is a simple way to give permission for further attacks.”