For four years I was the foreign minister of Lithuania, a country that was once occupied by the Soviet Union and is now a member of NATO and the European Union. Lithuania is on the eastern flank of democratic Europe, between Belarus and the Russian exclave of Kaliningrad. The Suwalki Gap, a 40-mile land corridor connecting us with our Polish friends, is regularly cited as the place where President Vladimir Putin of Russia would begin were he to start a war against NATO.

In this neighborhood, a foreign minister understands the importance of deterrence very well. Building alliances and maintaining partnerships with other democracies is not a matter of preference but of survival. We rely on collective defense — the rules of international law and human rights built by earlier generations. And we know that if that system breaks down, we will be among the first victims of its violent replacement.

President Trump is changing those rules. As he re-evaluates old relationships and forms new ones, it’s becoming clear that nothing succeeds with him quite like success. When longtime allies like Europe and NATO make overtures to him citing precedent, shared history or ideals, those appeals do not resonate. But, as Ukraine has shown, the sheen of a winner does appeal to the president. If Europe wants a better relationship with Mr. Trump, it should start acting like a winner.

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