A new book by journalists Bob Woodward and Robert Costa contains a singularly startling allegation. In the waning weeks of the Trump administration, Gen. Mark Milley, chairman of the Joint Chiefs of Staff, twice called his counterpart, Gen. Li Zuocheng, of the People’s Liberation Army, offering assurances that the United States was not about to launch an attack against China.

“If we’re going to attack,” Milley told Li, according to Woodward and Costa, “I’m going to call you ahead of time. It’s not going to be a surprise.”

The surprise turns out to be the revelation of Milley’s actions. Some in the Defense Department may have known about the calls, but one thing seems clear: President Trump, the U.S. commander in chief, did not. Milley acted of his own volition, without prior presidential approval. On that point, Christopher Miller, then serving as acting Defense secretary, is emphatic, describing Milley’s actions to Fox News as a “disgraceful and unprecedented act of insubordination.”

Providing adversaries with advance notice of U.S. military actions does not number among the prescribed duties of the chairman of the joint chiefs. Arguably, the Woodward-Costa allegations, if accurately reported, qualify as treasonous. At the very least, they raise serious doubts about Milley’s respect for the bedrock principle of civilian control of the military. To state the matter bluntly, when adherence to that principle raised the possibility of an outcome not to Milley’s liking, he seemingly granted himself an exemption.

Of course, all of this happened in a specific context: Woodward and Costa’s chilling account is only the latest to depict the unraveling Trump presidency following the November election. Unwilling to accept defeat, the incumbent all but ceased to govern and instead devoted himself to overturning the election’s results by any means necessary, violating the rule of law and waiving the Constitution.

Milley’s response, however, shouldn’t have been to do likewise.

By statute, the chairman of the Joint Chiefs of Staff advises the commander-in-chief. Choosing to accept, amend or disregard that advice, the president then decides, with military leaders obliged to implement those decisions. Through his communications with the Chinese general, Milley signaled his intention to forestall or undermine a presidential decision not to his liking. Opposing a possible war with China, Milley exerted himself to prevent Trump from starting one, communicating his intentions to Chinese authorities while the American people were kept in the dark.

Was Trump contemplating an attack on China? We don’t know; Trump himself denies it. Would any such attack have produced disastrous results, as Milley seems to have feared? Almost certainly. Yet while allowing that Milley’s intentions may have been honorable, his actions were categorically wrong and set a dangerous precedent.

But let’s be clear about where the problem lies: It’s with the existing U.S. system for controlling the use of nuclear weapons. That system placed Milley in a difficult predicament. Since the dawn of the nuclear era, Americans have entrusted presidents with the authority to initiate Armageddon on their own. Even though held in abeyance since Hiroshima and Nagasaki in 1945, that authority may well stand as the ultimate symbol of the power invested in the U.S. presidency.

The practice is also bizarre and dangerous in the extreme, as the meltdown that concluded the Trump presidency should remind us. And to suggest that Trump’s departure from office eliminates that danger overlooks the very real possibility that another Trump-like figure — or Trump himself — may win the White House again. Americans are not immune from conferring the presidency on figures who may not be models of stability and good sense.

If the United States is intent on maintaining at the ready a large nuclear strike force, as is apparently the case, the nation needs comprehensive safeguards to prevent reckless and ill-considered decisions regarding their use. We should not have to rely on American generals exerting themselves to check presidents who appear to have gone off the rails.

The essential fix is clear: Congress should act to curb the president’s authority to employ nuclear weapons, requiring decisions on the use of nuclear weapons to be made collectively rather than by a single individual, with senior military officers still obliged to stay in their lane.

A useful first step would be for the Senate and House to pass the Restricting First Use of Nuclear Weapons Act of 2021, sponsored by Sen. Edward J. Markey (D-Mass.) and Rep. Ted Lieu (D-Torrance). The bill would not prevent actions to defend the United States, but it would prohibit any president from launching a nuclear first strike without a prior congressional declaration of war. Sadly, there are few indications that our legislators with their pronounced aversion to collective responsibility will take up this issue anytime soon.

Milley’s questionable regard for the principle of civilian control was wrong and should be condemned. Yet given what we are learning know about Trump’s state of mind during the last weeks of his presidency, Milley’s actions also qualified as prudent. “It is breathtaking to think of the lengths that Milley and others went to avert the disasters Trump was creating at the end of his presidency,” Sen. Richard J. Durbin (D-Ill.) told reporters.

Perhaps so. But Milley’s audacity is hardly less breathtaking. It could well be that the nation owes the general a considerable debt of gratitude. Although President Biden has expressed his continuing confidence in Milley, his clear duty is to fire the general forthwith.

Andrew Bacevich, a retired Army colonel, is president of the Quincy Institute for Responsible Statecraft. His most recent book is “After the Apocalypse: America’s Role in a World Transformed.” he is a contributing writer to Opinion.