For more than 50 years, the specter of “the button” has haunted conversations about American nuclear weapons. While the power to launch nuclear war has—contrary to our imaginations— never actually been contained within a button, historian Alex Wellerstein says the idea of it reflects the way the American public sees this presidential power.

“There’s no one button. There never has been. There never should be. It’s a terrible idea,” he says. “It’s a metaphor for how we think about technology, simplicity and our lack of control.”

The idea of a button that can swiftly destroy countries, or even the world, hearkens back to a time even before the advent of nuclear weaponry. The earliest reference that Wellerstein found in his research is a satirical French story from the 1980s, which told of inventor Thomas Edison pressing a button that destroyed the world with electricity. During the 1920s, physicists dismissed the premise of a button that could end humanity as farfetched. World War II mainstreamed the idea of a “push-button war,” but once combined with the now real threat of nuclear implosion, it hardened in the public’s mind and popular culture perpetuated the myth.

To Wellerstein, the idea that nuclear-level destruction could be accomplished by an act as simple as the pressing a button reflects the impersonal terror of nuclear weaponry that has shaped world politics since it was first introduced in August 1945. Every president since then has had the power to order the use of a nuclear weapon, although only Truman has used it. That unique ability has helped to shape the modern presidency.

Today’s vision of a Commander-in-Chief personally spearheading the call to use a nuclear weapon is something that evolved over time, says Wellerstein. Initially, that decision was led by the military and the people directly under him. Few had given much serious thought to why control of nuclear weaponry should be different from control of more conventional weapons.

Over time, Truman himself as well as his biographers gave the impression, directly and indirectly, that he explicitly ordered the dropping of the bomb. The reality is that although Truman verbally approved the military order to drop nuclear bombs on Japan, says Wellerstein, the military order was drafted by General Leslie Groves, the officer who directed the Manhattan Project, and signed by Secretary of War Henry Stimson.

After the bombings of Hiroshima and Nagaski, however, Truman changed tack. “He suddenly seems to realize that this is something that he doesn’t want to delegate to the military,” Wellerstein says. Historian William Johnston writes that Truman’s first “explicit decision” about the bomb came on August 10, 1945, one day after the bombing of Nagasaki.

At that time, a third bomb drop had already been scheduled. A memo from Groves to General George C. Marshall, Chief of Staff of the Army, stated that “the next bomb of the implosion type had been scheduled to be ready for delivery on the target on the first good weather after 24 August 1945.” Scrawled along the bottom of that memo, however, is a note: “It is not to be released over Japan without express authority from the President.”

Truman thought the idea of killing “another 100,000 people was too horrible,” wrote Henry Wallace, secretary of commerce, in his diary. By taking personal responsibility for the launch order, he started a tradition of the president being the last word on the use of nukes, but it wasn’t a formal arrangement.

In November 1950, in the early months of the Korean War, Truman indicated that he would consider using nuclear weapons, writes scholar Se Young Jang. At a press conference, the President raised this possibility; he also implied that military commanders would have control over the weapon. Reporters questioned the idea of giving nuclear authority to the military, in particular the infamously hotheaded General Douglas MacArthur. Public outcry was swift, according to Jang. As a result of this incident, the White House quickly released a statement saying that “only the President can authorize the use of the atom bomb, and no such authorization has been given."

Even when MacArthur later requested nuclear bombs as a military option, Truman never authorized their use, helping to strengthen this presidential power, she writes. But it remained an “area of authority,” not something enshrined in law–despite the White House statement indicating otherwise.

The nature of the weapons the president controlled had changed rapidly after Hiroshima and Nagasaki. By 1948, new kinds of nuclear weapons were being tested by the Atomic Energy Commission, the successor to the Manhattan Project. In late 1952, writes the Department of Energy’s Alice Buck, thermonuclear weapons were first tested. By the time President Dwight D. Eisenhower took office in 1953, the United States held hundreds of nuclear bombs, some of them located in friendly foreign nations nearer to Russia. The methods of delivery had advanced greatly in that time as well. During World War II, the only delivery method for the nuclear bomb was an airplane with limited fuel capacity, and the weapon itself had to be assembled by hand by a highly skilled technician, Wellerstein says. But by the time Truman left office, the United States military had a jet bomber capable of flying much faster with mid-air refueling capabilty, as well as a nuclear surface-to-surface rocket.

The rapid pace of nuclear proliferation, combined with the knowledge that the Soviet Union also had nuclear weapons, helped shape Eisenhower-era decisions that empowered certain military officers to order a nuclear attack without the direct consent of the President. This policy was supposed to cover situations like the death of the President in an attack or a communications breakdown, writes Eric Schlosser in The New Yorker, but it also created the possibility of a situation frighteningly like that captured in the 1964 film Dr. Strangelove, where a rogue general orders a nuclear strike.

“It depends on what you value and what you want and what you’re most afraid of,” says Wellerstein. “And under Eisenhower, they are more afraid of the possibility of a Soviet surprise attack than they are of, say, a rogue general.”

By the time President John F. Kennedy took office in 1961, there was a growing discomfort with the idea of this lack of control. “There are a lot of details we still don’t know because they’re classified,” says Wellerstein. But overall, Kennedy’s administration created a system dictating how the nuclear bomb could be ordered and deployed.

“It should be noted that this is all through directives and regulations and secret directives. This is not through, like, laws,” he says. This makes interpreting the history difficult, he says, but also means that “policy can change fairly dramatically from administration to administration.”

Historians have been able to piece together a lot of information nonetheless. The Kennedy administration placed better safeguards on weapons deployed both inside and outside the United States, installing locks known as Permissive Action Links meant to prevent, say, a member of the military from launching a nuclear weapon without presidential clearance, or the nations hosting American weapons from seizing the technology for themselves

The Kennedy administration also created the Single Integrated Operating Plan, a unified plan for what to do in the case of nuclear war, a version of which is still in use today.

Before the creation of SIOP, each branch of the military had their own nuclear war plan, and they only had one option: massive destruction. Kennedy, building on work done at the end of the Eisenhower presidency, stipulated that the SIOP should contain multiple plans for attacks of different sizes, to help ameliorate the potential destruction and make nuclear war “more flexible.”

Kennedy had spoken out against nuclear weapons in the early days of his presidency and even before. Some of these changes were underway before the Cuban Missile Crisis of 1962, but that crisis sped up the pace of change and created greater incentive for the President to solidify the process for nuclear warfare.

These changes were “about streamlining and pulling together and centralizing a lot of this planning,” Wellerstein says, “and it centralizes it as all coming out of the presidency.” In 1962, Kennedy helped cement this image when he gave orders for the so-called nuclear “football” to follow him everywhere.

Some of the changes the Kennedy administration made took decades to fully implement, Wellerstein says, but the attitude of presidential control started in the 1960s. And after Kennedy’s assassination, his successor Lyndon B. Johnson perpetuated this way of seeing nuclear weapons. “By the time you have Johnson, it’s just assumed across the board, of course the president and only the president is in charge.”

In the time since the Truman administration, says Peter Feaver, a political scientist at Duke University, the process by which the president would order a nuclear strike has “become more robust and hardened” as well as being updated to take into account new ways of communicating, such as new phone technology. In some important ways, though, he says, “decisions that were made in the '40s have remained operative today.”

Truman’s decision to take control, for instance has endured. This significant maneuver, thereby vesting the power to order a nuclear strike in the hands of the president, a civilian authority, rather than to a high-ranking military official, remains critical to the debate over American nuclear warfare today.

“A decision to fire a bullet might be delegated down to many, many soldiers. A decision to fire a nuclear weapon could not,” says Feaver. “Nuclear weapons, or back then atomic weapons, were qualitatively different and required a civilian in the loop to make the political decision.”