New Delhi, Aug. 17 -- The exercise was scheduled to begin Monday morning, with 18,000 South Korean soldiers and roughly 5,000 American troops preparing for eleven days of joint drills across the peninsula. By Sunday evening, Washington had thrown the plan into uncertainty.

citing their cost and what he characterized as the hostile signal they send toward North Korea. Canceling the drills entirely was "too late," he acknowledged, so a partial reduction became the directive. The announcement landed with military planners in Seoul who had spent months designing the exercises and who did not learn of the decision in advance.

The Ulchi Freedom Shield drills were built around a specific operational purpose: to rehearse the combined command st...