President Trump’s nuclear saber rattling is a stark departure from his predecessors’ positions and could create major national security and diplomatic problems. (Jabin Botsford/The Washington Post)
James Cameron is a filmmaker, explorer and an adviser to both the Ocean Twilight Zone Audacious Project at the Woods Hole Oceanographic Institution and to the OceanX media initiative. He is currently in production on “Avatar 2.”

In less than a year in office, President Trump has significantly escalated U.S. rhetoric relating to nuclear weapons.

On Aug. 8, he threatened North Korea with “fire, fury and, frankly, power like this world has never seen.” Speaking to the U.N. General Assembly on Sept. 19, he vowed to “totally destroy North Korea” if necessary. In his next breath, he proclaimed that “Rocket Man,” the president’s name for North Korea’s leader Kim Jong Un, “is on a suicide mission for himself and for his regime.” According to reports, Trump’s inflammatory statements at the United Nations were not in a draft speech shown to senior members of his national security team.

Jarring enough when viewed in isolation, Trump’s off-the-cuff style is even more concerning when viewed in the context of past presidential behavior.

In contrast to Trump, who appears to make many of his nuclear threats impulsively, previous presidents carefully tailored their messages about U.S. nuclear policy in consultation with their senior advisers — even to the point of sometimes setting aside their personal doubts about American strategy.

They did so because presidential proclamations about nuclear weapons have a major effect on the public and America’s allies, and careless, ill-thought-out declarations threaten national security and the health of U.S. alliances.

No president better epitomized this tradition than John F. Kennedy. Had tragedy not struck on Nov. 22, 1963, Kennedy would have delivered a speech in Dallas that spotlighted the advances in U.S. nuclear weaponry that had taken place during his presidency, including a large buildup in ballistic missile submarines, land-based intercontinental ballistic missiles and bombers on alert. These developments, according to Kennedy’s speechwriters, had left the U.S. military “first” in the world.

Yet declassified records now suggest that Kennedy harbored real doubts that this nuclear buildup made the United States any safer.

During a December 1962 meeting with his closest advisers, Kennedy had questioned the wisdom of the buildup. “We have an awful lot of megatonnage to put on the Soviets [that is] sufficient to deter them from ever using nuclear weapons,” he said. “I don’t see quite why we’re building as many [nuclear weapons] as we’re building.” Reflecting on his experience just six weeks earlier during the Cuban missile crisis, Kennedy said he believed that “even what [the Soviets] had in Cuba alone would have been a substantial deterrent to me.”

At first glance, Kennedy’s behavior seems strange, even troubling. Why did he keep his doubts private? Should the commander in chief articulate a nuclear strategy about which he has misgivings?

The ensuing conversation, however, revealed precisely why Kennedy could not be forthcoming about his doubts, and why his personal feelings alone could not form the basis of American policy in this highly sensitive area.

Kennedy’s defense secretary, Robert S. McNamara, highlighted two rationales that pushed back against any change in the U.S. nuclear posture.

First, McNamara emphasized that the United States had to keep nuclear superiority to maintain the confidence of its NATO allies that the United States would come to their defense in the event of a Soviet attack.

Perhaps the United States could move away from superiority “someday,” McNamara argued, but the United States “could not change it today without seriously weakening the [NATO] alliance.” Any damage to NATO, American policymakers feared, could undermine the United States’ containment of the Soviet Union, leading to greater Soviet adventurism and increasing the risk of war.

The second danger McNamara highlighted was tied to the intersection of domestic politics and diplomacy.

McNamara told Kennedy that Curtis LeMay, the chief of staff of the Air Force, was already privately criticizing the nation’s nuclear forces as too weak. According to McNamara, this criticism left Kennedy with little choice but to declare that his policy was “maintaining nuclear superiority.”

Given the high stakes of the Cold War, Kennedy could not afford open criticism from the military about the strength of U.S. nuclear forces. In this area, perception was often reality. The publicly expressed opinions of authority figures such as LeMay, some of whom had very different views about nuclear might than Kennedy, were critical to the United States’ arsenal maintaining its deterrent capacity. In part to keep the generals appeased, U.S. nuclear posture remained unchanged at the time of Kennedy’s death.

The contrast between private feelings and public statements about nuclear weapons was not unique to Kennedy. Understanding the high international and domestic political stakes of U.S. nuclear strategy, Lyndon B. Johnson and Richard Nixon also refrained from publicly voicing misgivings regarding the U.S. posture.

Presidential nuclear rhetoric has therefore not traditionally been the unfiltered expression of the incumbent’s views on nuclear weapons and the potential to use them, but instead a carefully calibrated attempt to maintain both allied and domestic confidence in the U.S. government’s custodianship of the nation’s nuclear arsenal.

Measured by this standard, Trump is failing dismally. While allied officials have refrained from criticizing the president’s comments explicitly, local analysts have raised doubts about the credibility of U.S. strategy in the Trump era. “Trump doesn’t seem to understand what an alliance is, and doesn’t seem to consider his ally when he says those things,” said Lee Byong-chul, a South Korean nuclear scholar. “No American president has mentioned a military option so easily, so offhandedly as he has.”

Domestically Trump’s outbursts have led to questions about the president’s authority over nuclear weapons, unparalleled in recent times. Senate Foreign Relations Committee Chairman Bob Corker (R-Tenn.) has warned that Trump’s rhetoric risks putting the United States “on the path to World War III.” His committee has held hearings on the president’s power to unilaterally launch a nuclear strike, the first time Congress has probed this issue since the 1970s.

Whatever one thinks of current launch arrangements, the fact that these hearings are happening at all speaks to the deep concern on Capitol Hill regarding Trump’s nuclear posturing. The public shares this congressional discomfort. According to a Pew Research Center poll in August, 58 percent of Americans are not confident in Trump’s ability to “make wise decisions about the use of nuclear weapons.”

If the past is any guide, Trump needs to take greater account of both domestic and allied views on the acceptable limits of presidential nuclear rhetoric in the same way that Kennedy did. If he does not, then the growing doubts regarding the credibility of U.S. nuclear strategy could turn into a full-blown crisis at home and abroad.