Opposition leader Lee Jae-myung was sworn in as South Korea’s next president on Wednesday following a dramatic snap election six months after the country’s previous leader declared martial law and plunged the nation into chaos.

The U.S. ally has been without a permanent leader since late last year, when Yoon Suk Yeol was impeached over his botched declaration of martial law.

Lee faces the most daunting set of challenges for a South Korean leader in nearly three decades, ranging from healing a country scarred by the martial law attempt to tackling unpredictable U.S. protectionist moves.