SEOUL, Aug. 25 -- When South Korean Marine commanders reviewed their training calendar for the autumn, the gap where the Ssangyong exercise had been was already filled with contingency planning. The United States had sent word in June: the Marine Corps could not spare forces for the biennial amphibious landing drill - the joint exercise that Washington and Seoul have used for decades to signal their combined readiness to defend the Korean Peninsula. American forces were too stretched by the widening conflict in the Middle East.

The cancellation, confirmed this week by South Korean military officials, strips one of the most visible markers of the US-South Korea alliance from the 2026 training schedule. Han Seung-jeon, a spokesperson for t...