WARSAW—Polish leaders welcomed U.S. troops to their country Saturday, with the defense minister expressing gratitude for their arrival and calling it the fulfillment of a dream Poles have had for decades.

The ceremony in the western Polish town of Zagan comes some 23 years after the last Soviet troops left Poland. It marks a new historic moment—the first time Western forces are being deployed on a continuous basis to the North Atlantic Treaty Organization’s eastern flank. The move has infuriated Moscow.

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