Mr. Trump is considering his options, including some reduction of force. But even a partial U.S. retreat from the East Asian flashpoint would echo around the world as a sign of American weakness. It also wouldn’t save money since the Pentagon would have to pay the troops even if they come home, and it would cost far more to have to send those forces back to the region in a crisis.

Above all, a U.S. retreat would be a gift to the hawks in China who want to push the U.S. out of the region. Withdrawal would confirm their view that the U.S. is in decline and can no longer be trusted, and it would shock our allies in Japan and Taiwan.

Senator Ben Sasse, the Nebraska Republican, didn’t hold back Friday in criticizing the potential withdrawal: “This kind of strategic incompetence is Jimmy Carter-level weak. Why is this so hard? We don’t have missile systems in South Korea as a welfare program; we have troops and munitions there to protect Americans. Our aim is to give the Chinese communist leadership and the nuclear nut tyrannizing his North Korean subjects something to think about before they mess with us.”

As for the domestic U.S. politics, a withdrawal certainly doesn’t fit an election strategy of running against Joe Biden as a naif who’d be eaten alive by Chinese President Xi Jinping.