WASHINGTON -- As a candidate, Donald Trump boasted of his lack of government experience and argued his business background qualified him to handle a president's most august responsibility -- handling the nuclear arsenal.
On Sunday, hours after North Korea claimed it had tested its first hydrogen bomb, far more powerful than its previous nuclear tests, Defense Secretary James N. Mattis emerged from a meeting that Trump had just held with his top national security advisers, and raised the specter of nuclear war.
Standing in the White House driveway with Gen. Joseph F. Dunford, chairman of the Joint Chiefs of Staff, Mattis warned Pyongyang that aggression against the United States or its allies would trigger a unified world response and what he termed the "total annihilation of a country, namely North Korea."
"Any threat to the United States or its territory, including Guam, or our allies, will be met with a massive military response, a response both effective and overwhelming," Mattis said.
The warning was all the more severe because it came from Mattis, a retired Marine Corps general who had sought to tamp down so many of Trump's bellicose comments and tweets in recent weeks that he was forced to deny a split with the president.
Sunday's drama represented a new reality for Trump. His presidency has been defined largely by political crises of his own making, from his decision to fire FBI Director James B. Comey to his comments after racial violence in Charlottesville, Va. It was inevitable that circumstances outside his reach would complicate his tenure.
And now they have, raising the question of how he will handle a double-barreled pair of crises -- the growing threat from North Korea and the recovery and relief efforts for hundreds of thousands of Americans caught in epic floods in Texas and Louisiana.
To add to his challenges, the White House has said Trump will disclose Tuesday whether he will authorize the deportation of 800,000 so-called Dreamers, immigrants brought here illegally as children -- a decision that will be political combustible no matter what he decides.
Off in the wings are high-stakes battles that will begin Tuesday on Capitol Hill, including funding the government to avoid a shutdown by Sept. 30, raising the federal debt ceiling, and approving billions in aid for the victims of Hurricane Harvey's devastation.
Undergirding all these is special counsel Robert S. Mueller III's investigation of whether Trump's aides cooperated with Russian meddling in the 2016 presidential election. That probe has steadily gathered steam, even if pushed out of view in recent weeks.