1. United States
2. Ohio
3. Letter

On Monday morning, roughly 18,000 South Korean troops began an exercise built around the dangers they may actually face: drones crossing the border, GPS signals disappearing and cyberattacks disrupting military communications. North Korean soldiers have returned from Russia’s war against Ukraine with battlefield experience in these methods. Yet as Ulchi Freedom Shield got underway, the order from Washington was to scale it back—not because the threat had faded, but because South Korea declined to join Donald Trump’s war against Iran. Trump made the connection himself. He said he had asked South Korean President Lee Jae Myung to participate in the “denuclearization” of Iran and Seoul replied, “No thanks!” Trump then ordered the Pentagon to “substantially reduce” the exercise, while describing Kim Jong Un’s regime as “unthreatening and respectful.” In other words, a democratic ally refused the president’s request to enter an unrelated war, and as a result the president weakened a military exercise meant to protect the ally from a nuclear-armed dictatorship. I cannot read Trump’s explanation without getting angry. He is risking the readiness of American and South Korean troops because another president had the nerve to tell him no. South Korea’s president has his own country to answer to, and disagreement does not release America from its promises. Trump is behaving as though this alliance belongs to him personally. Training exposes failures while there is still time to fix them. It shows whether people from different units can communicate under pressure and whether plans will work outside the briefing room. When two countries may have to fight together, that preparation matters even more. American and South Korean forces cannot learn to fight together after the missiles start flying. The military understands this. United States Forces Korea describes these exercises as a way to test combined readiness and improve coordination under realistic conditions. Gen. Xavier Brunson, the commander of U.S. Forces Korea, put it plainly after a recent exercise: “There is no substitute for training, there is no excuse for not being ready.” Trump is gambling with the lives of American and South Korean troops because Seoul hurt his feelings. His excuse about burden-sharing is especially dishonest. Defense Secretary Pete Hegseth praised South Korea in May for increasing its defense spending and assuming greater responsibility for security on the peninsula. Hegseth said Seoul’s example was one that “all of America’s partners would do well to follow.” A few months later, the president is using military preparedness to punish the same ally because it wouldn’t join his failed war against Iran. To be clear, South Korea was under no obligation to do so. The mutual-defense treaty signed after the Korean War does not require Seoul to support every military campaign launched by an American president. And an ally should never have to join a war out of fear that Washington will punish it for saying no. Trump judges democratic partners by whether they flatter him and authoritarian adversaries by whether they make him feel important. Kim Jong Un understands this. He knows that a warm letter, a photograph and a few compliments have more influence on Trump than treaty commitments or the judgment of American commanders. After meeting Kim in Singapore in 2018, he adopted North Korea’s description of the exercises as “provocative” and announced that he would suspend them. American and South Korean officials were caught by surprise. Trump gave Kim something he had wanted for years and received no enforceable plan for denuclearization in return. The diplomacy eventually collapsed. The exercises resumed, and North Korea continued expanding its missile and nuclear capabilities. Earlier this month, it launched two more ballistic missiles. Trump has responded by praising Kim’s behavior and repeating the concession that failed eight years ago, except this time he has added a grievance against South Korea that has nothing to do with security on the peninsula. Trump is telling South Korea, Japan and every other American ally that they may not be able to count on us. If military cooperation can be reduced because a partner refuses to join an unrelated war, governments will begin preparing for the possibility that America will abandon them when they need us most. South Korea already has broad public support for building its own nuclear arsenal. If our allies decide they need nuclear weapons because they no longer trust Washington, our children will live with the consequences long after Trump is gone.