Defense Secretary James Mattis on Oct. 30 told the Senate Foreign Relations Committee how the US would respond to a North Korean nuclear missile attack.
“What happens if somebody knocks on the door of the Oval Office and says, ‘Mr. President, they’ve launched’?” Sen. Jim Risch said.
Mattis replied: “Our ballistic-missile-defense forces at sea and in Alaska and California … the various radars would be feeding in, and they would do what they’re designed to do as we make every effort to take them out.”
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The US has recently tested and improved its missile-defense systems, but the threat from a North Korean intercontinental ballistic missile remains a serious question, as experts have said the US wouldn’t fare well against a salvo of missiles or those with decoys or countermeasures.

But the bulk of US deterrence has never rested in missile defense, but rather in offensive capability.
“The response — if that’s what you’re referring to — would, of course, depend on the president,” Mattis said. He explained that the president would see a “wide array” of options that included cooperation with US allies.
“Defenses will go,” Mattis said. “The president will be woken up or whatever, but our commands are — we rehearse this routinely.”
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Secretary of State Rex Tillerson added: “Some judgment would be made over whether a necessary and proportionate response is required.”
But neither Tillerson nor Mattis would categorically rule out a nuclear first strike on North Korea. Both made statements to the effect that if the US knew a North Korean nuclear attack on the US was imminent, President Donald Trump reserved the right to preempt it with a launch.
“The fact is that no president, Republican or Democrat, has ever forsworn the first-strike capability,” Tillerson said. “That has served us for 70 years.”