WASHINGTON, Aug. 17 -- South Korea's Ministry of Defence announced Monday morning that its annual joint military exercises with the United States would proceed on schedule, hours after President Donald Trump ordered his Pentagon chief to "substantially reduce" the drills and accused them of being "totally inappropriate and hostile" toward North Korea.

The defiance was quiet, clinical, and immediate. A statement from Seoul said the Ulchi Freedom Shield exercises, which deploy some 18,000 South Korean troops alongside US forces for eleven days each summer, "will proceed as previously notified and scheduled." The statement did not mention Trump by name.

For Seoul, the order presents an impossible bind. South Korea is the country these exer...