AP Photo

WARSAW, Poland — The first of September, symbolic as the 70th anniversary of the start of World War II, also marked the end of an era of special closeness between Poland and the United States.

The dignitaries jostling for space near the Gdansk memorial where the opening shots of WWII were fired included Angela Merkel, the German chancellor, and Russian Prime Minister Vladimir Putin. The U.S. was represented by Gen. James Jones, the national security adviser.

Even Jones was a step up from the original suggestion: William Perry, the former defense secretary, according to Slawomir Nowak, a close adviser of Donald Tusk, Poland’s prime minister.

The low priority given by the U.S. to an event that was of huge symbolic importance to the Poles is a sign of...