Read an extract from Annie Jacobsen’s terrifying new book Nuclear War: A Scenario

A 1-megaton thermonuclear weapon detonation begins with a flash of light and heat so tremendous it is impossible for the human mind to comprehend. One hundred and eighty million degrees Fahrenheit is four or five times hotter than the temperature that occurs at the center of the Earth’s sun.

In the first fraction of a millisecond after this thermonuclear bomb strikes the Pentagon outside Washington, D.C., there is light. Soft X-ray light with a very short wavelength. The light superheats the surrounding air to millions of degrees, creating a massive fireball that expands at millions of miles per hour. Within a few seconds, this fireball increases to a diameter of a little more than a mile (5,700 feet across), its light and heat so intense that concrete surfaces explode, metal objects melt or evaporate, stone shatters, humans instantaneously convert into combusting carbon.

The five-story, five-sided structure of the Pentagon and everything inside its 6.5 million square feet of office space explodes into superheated dust from the initial flash of light and heat, all the walls shattering with the near-simultaneous arrival of the shock wave, all 27,000 employees perishing instantly.

Not a single thing in the fireball remains.

Nothing.

Ground zero is zeroed.

It has been three seconds since the initial blast. There is a baseball game going on two and a half miles due west at Nationals Park. The clothes on a majority of the 35,000 people watching the game catch on fire. Those who don’t quickly burn to death suffer intense third-degree burns. Their bodies get stripped of the outer layer of skin, exposing bloody dermis underneath.

Third-degree burns require immediate specialized care and often limb amputation to prevent death. Here inside Nationals Park there might be a few thousand people who somehow survive initially. They were inside buying food, or using the bathrooms indoors—people who now desperately need a bed at a burn treatment center. But there are only ten specialized burn beds in the entire Washington metropolitan area, at the MedStar Washington Hospital’s Burn Center in central D.C. And because this facility is about five miles northeast of the Pentagon, it no longer functions, if it even exists. At the Johns Hopkins Burn Center, forty-five miles northeast, in Baltimore, there are less than twenty specialized burn beds, but they all are about to become filled. In total there are only around 2,000 specialized burn unit beds in all fifty states at any given time.

Within seconds, thermal radiation from this 1-megaton nuclear bomb attack on the Pentagon has deeply burned the skin on roughly 1 million more people, 90 percent of whom will die. Defense scientists and academics alike have spent decades doing this math. Most won’t make it more than a few steps from where they happen to be standing when the bomb detonates. They become what civil defense experts referred to in the 1950s, when these gruesome calculations first came to be, as “Dead When Found.”

Humans created the nuclear weapon in the twentieth century to save the world from evil, and now, in the twenty-first century, the nuclear weapon is about to destroy the world. To burn it all down.

Nuclear War: A Scenario by Annie Jacobsen, published by Torva (£20.00), is available now. It is the latest pick for the New Scientist Book Club: sign up here to read along with our members