As a storm bore down on Osaka on Thursday, bringing heavy rains to the city ahead of the Group of 20 summit, another was on its way — straight from Washington.

Osaka was gearing up for the two-day gathering of world leaders that kicks off Friday, with Prime Minister Shinzo Abe hoping for a conference with as few hitches as possible. But even before the summit got underway, an obstacle to that goal emerged in the form of Abe's "golf buddy": U.S. President Donald Trump.

Ahead of his departure for a rain-drenched Osaka, Trump indiscriminately lobbed verbal grenades at both his enemies and closest allies, appearing to reignite a controversy over an earlier report that he was considering the possibility of terminating the postwar defense pact with Japan — the backbone of the alliance between the two countries.