Before U.S. President Donald Trump took office on Jan. 20 last year, Japanese officials were anxious, even obsessed, with a nightmare scenario that could not be ruled out — an incoming American leader who could shake up the balance of power in the Asia-Pacific region and vastly damage domestic interests.

During his election campaign, Trump threatened to withdraw U.S. forces from Japan unless Tokyo paid all stationing costs and hinted that he would let Japan and South Korea arm themselves with nuclear weapons, which would strain regional tensions and could even spur an arms race in East Asia.

The former reality TV star also vocally pledged to launch a trade war with Tokyo to cut the U.S. trade deficit, reviving bitter memories of the long-running diplomatic battles Tokyo and Washington waged in the 1980s and '90s.