Tuesday’s Senate Foreign Relations Committee hearing on the use of nuclear weapons highlighted the acute danger of the eruption of a war that could kill hundreds of millions or even billions of people.

The hearing was called amid a series of threats by the Trump administration to go to war with North Korea. In addition to Trump’s threats to unleash “fire and fury like the world has never seen” against a country whose economy is one one-thousandth the size of America’s, National Security Advisor H. R. McMaster, an active duty Army general, has made clear that the US is prepared to wage a “preventive,” that is, unprovoked, war.

To back up this threat, the Trump administration has deployed a vast armada off of the Korean Peninsula, including three aircraft carrier battle groups and an array of nuclear-capable submarines and bombers. At the same time, Washington is moving to expand and modernize the US nuclear arsenal.

Speaking at Tuesday’s hearing, Massachusetts Senator Ed Markey declared that plans could be in place “right now in the White House given to the president to launch a preemptive war against North Korea using American nuclear weapons without consulting with, informing Congress.”

Senator Chris Murphy of Connecticut said Congress was “concerned that the president is so unstable, is so volatile, has a decision-making process that is so quixotic, that he might order a nuclear weapons strike” on a whim.