WASHINGTON — Here’s a question rarely raised before Donald Trump ran for the White House: If the president ordered a pre-emptive nuclear strike, could anyone stop him?

The answer is no.

Not the Congress. Not his secretary of defense. And by design, not the military officers who would be duty-bound to execute the order.

As Bruce Blair, a former nuclear missile launch officer and expert on nuclear command and control, has put it, “The protocol for ordering the use of nuclear weapons endows every president with civilization-ending power.”

Trump, he wrote in a Washington Post column last summer, “has unchecked authority to order a preventive nuclear strike against any nation he wants with a single verbal direction to the Pentagon war room.”

Or, as then-Vice President Dick Cheney explained in December 2008, the president “could launch a kind of devastating attack the world’s never seen. He doesn’t have to check with anybody. He doesn’t have to call the Congress. He doesn’t have to check with the courts.”

And the world has changed even more in the decade since, with North Korea posing a bigger and more immediate nuclear threat than had seemed possible.

The nature of the U.S. political world has changed, too, and Trump’s opponents – even within his own party – question whether he has too much power over nuclear weapons.

These realities will converge Tuesday in a Senate hearing room where the Foreign Relations Committee – headed by one of Trump’s strongest Republican critics, Sen. Bob Corker of Tennessee – will hear testimony from a former commander of the Pentagon’s nuclear war fighting command and other witnesses. The topic: “Authority to order the use of nuclear weapons.”

Corker said numerous lawmakers have raised questions about legislative and presidential war-making authorities and the use of America’s nuclear arsenal.

“This discussion is long overdue,” Corker said in announcing the hearing.

Some aspects of presidential nuclear war-making powers are secret and therefore not well understood by the public. The system is built for fast decision-making, not debate.

That’s because speed is seen as essential in a crisis with a nuclear peer like Russia. Unlike North Korea, Russia has enough nuclear weapons to destroy the U.S. in minutes.

Russia’s long-range missiles could reach the U.S. in about 30 minutes. Submarine-launched missiles fired from nearer U.S. shores might arrive in half that time.