South Korea’s political crisis shows no sign of abating. President Yoon Suk Yeol’s impeachment and impending arrest will usher in months of leadership uncertainty. The chaos will be welcomed by China and North Korea, but for the U.S., its influence with a key ally is at risk.

Yoon has said he will fight to stay on, despite his disastrous declaration of martial law late on Dec. 3, but he is unlikely to succeed. The Constitutional Court has 180 days to decide whether to accept the impeachment motion passed by the National Assembly as legal. If it does, the leader will be ousted and elections must be held in 60 days.

His loss will be destabilizing for the U.S. Yoon was a key driver in the South Korea, Japan and U.S. trilateral alliance, designed to boost regional security in the face of China’s expansionism and North Korea’s belligerence. Joint U.S.-Korea training on submarine hunting and sharing real-time data on ballistic missile launches to ward off potential threats from Pyongyang were among his biggest achievements.