STUTTGART, Germany — Defense Secretary Ash Carter used his address at a change-of-command ceremony here on Tuesday to warn Moscow: If you start a war, the U.S. can make sure you regret it.

Carter was in Germany to welcome Gen. Curtis Scaparrotti as the new head of U.S. European Command, who replaces Gen. Philip Breedlove. Carter, who did not name Russia (but his implication was clear), said the U.S. must prioritize deterrence in Eastern Europe following Russia’s aggressive actions in Ukraine, Georgia and Moldova.