WASHINGTON — The Defense Department has abruptly canceled the deployment of more than 4,000 troops to Poland, three U.S. Army officials said Thursday, part of a realignment of American forces in Europe announced this month that has caught many military officials off guard. Two weeks ago, the Pentagon said it was withdrawing 5,000 troops from Germany and would redeploy them to the United States and other posts overseas. It also canceled a plan developed under the Biden administration to place a missile-equipped artillery unit in Europe. Those decisions came after President Donald Trump angrily responded to remarks by Germany’s chancellor, Friedrich Merz, that Iran had “humiliated” the United States. Merz questioned how Trump planned to end that conflict. It was unclear why Defense Secretary Pete Hegseth canceled the deployment to Poland, which has close relations with the United States and had been considered a possible location for some of the forces leaving Germany. There are now about 7,400 U.S.…