When Harry S. Truman became president in April 1945, military advisors briefed him on the coming advent of the atomic bomb.

In July, shortly after the first successful nuclear test blast, Truman wrote in his personal diary that Japanese "soldiers and sailors" would be the future targets, "not women and children."

This may be why he initially hailed the August bombings of Hiroshima and Nagasaki — targets chosen by and attacked on authority of the US military — as great successes.

"Nobody ever goes to Truman and says, 'should we do this?' They go to him and they say, 'we are doing this,'" Alex Wellerstein, an author and nuclear history expert, said in a new episode of Radiolab released Friday, titled "Nukes".

But Truman quickly learned they were cities packed with women and children, then asked his generals to halt a third atomic strike in the works.

"He has immediately written back to them, and says, 'Just stop, knock it off. You are not going to drop another bomb without expressed permission of the president of the United Sates,'" Wellerstein said.

The Radiolab episode explores the question of who or what — if anyone or anything — can stop a US president today from launching a nuclear weapon. It turns out Truman's push for presidential (and civilian) control over nuclear weapons stuck, but with a very big catch.

"The system is set up so that only the president has the authority to order a nuclear war. Nobody has the right to countermand that decision," William J. Perry, the 19th Secretary of State who served under former President Bill Clinton, from 1994 to 1997, told Radiolab.

"He might choose to call the Secretary of Defense or the Secretary of State, or the Chairman of the Joint Chiefs of Staff, to get his advisors' counsel," Perry added. "But even if he does that, he may or may not accept that counsel."

Permission to nuke not required

A military aide carries the "Football", a leather briefcase stocked with the classified nuclear war plans. Cliff Owen/AP

The single-handed authority of the US president to use his "nuclear football" has been public knowledge for decades.

But current world affairs are refocusing attention on the policy.

President Donald Trump has spoken about expanding the US nuclear arsenal and, in regard to Russia's weapons program developments, has said "let it be an arms race." He's also inherited a $1 trillion program to modernize US nukes as North Korea expands tests of systems that could carry and detonate nuclear weapons. And on April 6, Trump ordered a retaliatory strike against Bashar Assad's regime in Syria — a close ally with Russia, which is a nuclear superpower.

A global nuclear exchange could annihilate hundreds of millions of lives and sour Earth's atmosphere, water, and ground for generations.

Robert Krulwich, one of Radiolab's hosts, asked Perry further about the checks and balances of the president' first-strike capability. Their conversation was revealing:

Krulwich: "If you as Secretary of Defense say to the president — he says, 'let's go,' and you say, 'let's not,' can you…"

Perry: "First of all, if he calls me, and then if I say, 'Mr. President, that would be a very serious mistake, don't do that,' he might or might not accept my advice."

Krulwich: "Are you necessary to launch?"

Perry: "No."

Krulwich: "Suppose everybody in the room thought it was a bad idea. Would he still be able to do it?"

Perry: "Yes. He has the call directly to the Strategic Air Command to do the launching, and they will respond to his orders. They don't call the Secretary of Defense or the Chairman [of the Joint Chiefs of Staff] and say, 'should I do this?' They do it."

You can listen to Radiolab's full 56-minute episode below:



The audio highlights protest legislation introduced by Rep. Ted W. Lieu and Sen. Edward J. Markey (both Democrats) to curb the president's nuclear-strike powers. The bills, drafted before Trump became president, "would prohibit the President from launching a nuclear first strike without a declaration of war by Congress," according to a January 2017 press release.

But the episode mainly focuses on the story of Maj. Harold L. Hering.

Hering aged out of flying helicopters during the Vietnam War and decided to take a job as a missilier: one of many pairs of people in bunkers across the US that can launch intercontinental ballistic missiles tipped with nuclear warheads.

During his missilier training, Hering asked who or what is checking or balancing the president, who may be mentally or morally unfit to make the call — and the rest of the tale is fascinating history.