The Pentagon in late February simulated a “limited” nuclear exchange between U.S. and Russian forces. In other words, a small atomic war.

The simulation -- more accurately, the Pentagon’s revelation of the simulation -- appears to be part of the U.S. Defense Department’s effort to secure from Congress billions of dollars in additional funding for new, low-yield nukes.

Some theorists believe low-yield weapons are more useful than high-yield weapons are. But it’s important to note that even a “small” nuclear war would kill tens of millions of people and fundamentally alter life on Earth.

The nuke-war simulation occurred during Secretary of Defense Mark Esper’s visit to the headquarters of U.S. Strategic Command in Omaha, Nebraska.

“We conducted a -- a mini-exercise, if you will,” an unnamed “senior defense official” explained in a press conference at the Pentagon.

“The scenario included a European contingency where you are conducting a war with Russia, and Russia decides to use a low-yield limited nuclear weapon against a site on NATO territory, and then you go through the conversation that you would have with the secretary of defense and then with the president, ultimately, to decide how to respond,” the official said.

“And so they played out that game, and the secretary got a good understanding for how that went.”

But even a small nuclear war would kill or injure nearly 100 million people within just a few hours, a team of researchers at Princeton University concluded when they simulated an exchange of low-yield “tactical” nuclear weapons between the United States and Russia.

Princeton’s Science and Global Security project team on Sept. 6, 2019 released a video of the simulation, with tiny missiles arcing over continental maps and pinprick blasts erasing cities and countries as the body-count rises.

The video underscores what experts for years have been saying. There’s really no such thing as a small nuclear war. Any wartime use of atomic weapons would be catastrophic, even civilization-ending.

The Science and Global Security team developed the simulation to depict what it described as “a plausible escalating war between the United States and Russia using realistic nuclear force postures, targets and fatality estimates. It is estimated that there would be more than 90 million people dead and injured within the first few hours of the conflict.”

The Princeton simulation relies in part on NUKEMAP, an on-line atomic-strike simulator that historian Alex Wellerstein developed. “We live in a world where nuclear weapons issues are on the front pages of our newspapers on a regular basis, yet most people still have a very bad sense of what an exploding nuclear weapon can actually do,” Wellerstein explained.

“This project is motivated by the need to highlight the potentially catastrophic consequences of current U.S. and Russian nuclear-war plans,” the Princeton team stated.

“The risk of nuclear war has increased dramatically in the past two years as the United States and Russia have abandoned long-standing nuclear arms control treaties, started to develop new kinds of nuclear weapons and expanded the circumstances in which they might use nuclear weapons.”

As part of the wider strategic escalation between the two countries, the United States under Pres. Donald Trump has moved to acquire new, smaller-yield nuclear weapons -- and has begun writing doctrine for employing them even in cases where the threat is non-nuclear.

This is a bad idea, Deverrick Holmes explained for the Center for Arms Control and Non-Proliferation in Washington, D.C. “Embracing the concept of limited nuclear war is folly to the highest degree, and we fool ourselves if we think using low-yield nuclear weapons will somehow help halt the escalation to all-out destruction.”

The February 2020 war game coincided with the first-ever deployment, aboard a U.S. Navy Ohio-class submarine, of the Pentagon’s new W76-2 low-yield atomic warhead.

Hans Kristensen, the director of the nuclear information project at the Federation of American Scientists, told The Guardian that it was unusual for the military to provide so much information on a nuclear war game. The motivation appears to be budgetary.

“Remember, it’s only a few weeks ago that we had the official confirmation that this new [W76-2] low-yield warhead had been deployed,” Kristensen said. “And we’re now moving into a new budget phase where they have to go to Congress and try to justify the next new nuclear weapon that has a low-yield capability which is a sea-launched cruise missile. So all of this has been played up to serve that process.”

David Axe serves as Defense Editor of the National Interest. He is the author of the graphic novels  War Fix, War Is Boring and Machete Squad.