This story was published in partnership with The Center for Public Integrity. This is the seventh in a 10-part series on nuclear risk, military technology and the future of warfare in light of Russia’s invasion of Ukraine.

Russia’s war on Ukraine has brought renewed attention to tactical nuclear weapons, with the White House announcing on March 24 that it had a team of experts briefing NATO on contingency plans in case any such weapon is used. 

As a defensive alliance, NATO has formally stayed out of the war, though many member countries have sent military supplies to Ukraine, from tiny Luxembourg to the United States. 

According to a March 23 New York Times report, this contingency planning included options for what might happen if Russia used a “small” tactical nuclear bomb. These shorter-range weapons, often with small yields, are known as tactical nuclear weapons. Developed early in the Cold War and still in existence now, these weapons persist as part of the broader nuclear arsenals of the U.S. and Russia. 

On March 28, Dmitry Peskov, a spokesman for the Kremlin, told PBS that “no one is thinking about using, about even the idea of using a nuclear weapon.” 

But the war offers a good moment to take a look at just what a tactical nuclear weapon is, and how they differ from the kinds of warheads that are in ICBMs. From the dawn of the Cold War in the 1940s through the 1980s, both the U.S. and the Soviet Union invested tremendous amounts of time, energy and resources strategizing around nuclear weapons with the expectation that they would be used in a war over Europe. This led first the United States, and then the USSR, to develop and field nuclear weapons for the battlefield.

No nation has detonated a nuclear weapon in war since the U.S. did so twice over the Japanese cities of Hiroshima and Nagasaki in August 1945, killing as many as 210,000 people. That destructive power, carried compactly in the bays of just two bomber planes, had no special taboo against its use until President Harry Truman made the decision for the Army to stop using it.

Little Boy, the atomic bomb dropped on Hiroshima, had a yield of 15 kilotons, or the equivalent of 15,000 tons of TNT. Fat Man, the atomic bomb dropped on Nagasaki, had a yield of 21 kilotons. These attacks followed the Trinity Test, and preceded hundreds of nuclear tests by the United States in Nevada and across Pacific islands, many of which spread fallout on the people downwind of the blasts.

The Soviet Union tested its first nuclear weapon in 1949, and both nations went on to develop hydrogen bombs, or thermonuclear weapons, which use fusion reactions to create much more explosive yields than the fission reactions of atomic warheads. The U.S. detonated its first thermonuclear device as part of Operation Ivy in 1952  at Enewetak Atoll in the Marshall Islands; it had a yield equivalent to 10.4 million tons of TNT. 

Thermonuclear weapons were designed for total war, capable of destroying whole cities on a scale far outpacing the devastation wrought on Hiroshima and Nagasaki. Carried by long-range bombers and, later, intercontinental ballistic missiles fired from submarines, underground silos, and mobile launcher vehicles, these became the strategic nuclear weapons. In 1960, the administration of President Dwight Eisenhower put together its strategy, classified until 2004, for overwhelming nuclear assault on cities in the Soviet Union and its allied countries in the event of a war, based on the power and multitude of U.S. nuclear weapons. 

A brief but terrifying history of tactical nuclear weapons
The M65 artillery piece was also known as Atomic Annie. It’s seen here in 2017, when it was set to go in display at the Ordnance Training Support Facility in Fort Lee, Virginia. US Army / Terrance Bell

Tactical nuclear weapons

At the same time that the U.S. was developing these powerful warheads for long-range nuclear attacks, it was also working on smaller, shorter-range weapons that could function as a kind of super artillery if Soviet armies attacked into Europe. One of the more infamous of these tactical weapons was the “Atomic Annie,” a large artillery piece deployed to Europe in the 1950s. The cannon could fire a 15-kiloton nuclear warhead a distance of over 18 miles. By contrast, the Enola Gay B-29 bomber, which dropped the 15-kiloton warhead on Hiroshima, could fly 2,900 miles to a target before having to turn around.

Then there was the Davy Crockett warhead, which had a yield equivalent to just 20 tons of TNT. The recoilless rifle that fired it had an even shorter range than the Atomic Annie, up to just 2.5 miles. The shortest-range tactical nuclear device was the Special Atomic Demolition Munition, which was functionally a backpack-carried bomb designed to be set in place and detonated, in what was assumed to be a suicide mission.

The U.S. Army would eventually replace these nuclear novelties with warheads on short-range rockets, designed for use in battle. The weapons were deployed with the U.S. military in Europe, in part, to indicate a willingness to use American nuclear weapons to defend European countries.

NATO, still a young alliance in the 1950s and ‘60s, was backed by the strength of the American military, but most U.S. forces were at least one ocean away. The USSR-led Warsaw Pact bordered the countries in which both alliances assumed any war in Europe would be fought, most especially West Germany. The USSR had the numbers of soldiers, tanks, and artillery on the ground to win a conventional war. U.S. nuclear weapons were proposed as a way to even those odds, but European allies had to be convinced that the U.S. would risk a nuclear war to defend Europe. 

Deploying short-range tactical nuclear weapons in the path of any Soviet advance, wrote Tom Nichols, professor at the Naval War College, “warned the Soviets, in effect, that if Europe were invaded, the choice to use nuclear arms would be forced upon NATO by the successes of the Red Army.”

Had such an invasion ever come, the commanders in the field, given authorization to use nuclear weapons to avert defeat, would retreat after deployment. (Soviet plans for war were to specifically attack tactical nuclear sites.) The war would then either end in hours with an exchange of ICBMs, or with a ceasefire negotiated to prevent armageddon.

The escalation ladder 

Defense intellectuals describe the steps between peace and thermonuclear oblivion through an “escalation ladder,” with the leadership of both countries at war taking actions that invite the other country to either escalate, by increasing the stakes and tensions, or de-escalate, by backing away from further conflict. Tactical nuclear weapons are the rung separating conventional battle from a nuclear war.

Soviet leaders developed their nuclear weapons and doctrine as a response to U.S. nuclear war planning, and awareness of U.S. nuclear deployments to Europe. Both the U.S. and USSR assumed that once tactical nuclear weapons were used, it was more likely that thermonuclear exchange, not deescalation, would follow.

“As we now know, the Soviet High Command wrestled with this dilemma, since taking a Europe in ashes defeated the whole point of invasion in the first place,” Nichols wrote. “They worked out their own plans for first-use of tactical nuclear arms, for massive use of tactical arms, and for nuclear retaliation. All of the options led to the same dead end of escalation, strategic retaliation, and catastrophe.”

That the inevitable end of a war in which tactical nuclear weapons are used is a catastrophe did not prevent the Soviet Union from developing the weapons, much as the U.S. had. Soviet tactical nuclear weapons included suitcase bombs, nuclear mines, nuclear artillery shells, missiles, short-range missiles fired from planes, and air-dropped bombs. Like the U.S, the USSR deployed its nonstrategic nuclear weapons at bases in allied countries.

Many of these weapons still exist. The U.S. legacy of tactical nuclear weapons continues with 100 B61 nuclear bombs deployed at bases in Europe. The B61 bomb, currently in the process of being upgraded, can be carried by a range of fighter jets, as well as inside B-2 bombers. The B61 is also the smallest yield of any nuclear weapon presently in the U.S. arsenal. Under the B61 mod 12, that yield can be toggled from a low of 300 tons to a maximum of 50 kilotons, the latter of which would make it 3.3 times as powerful as Little Boy, the bomb dropped on Hiroshima. 

Russia, which inherited the nuclear weapons of the Soviet Union, has had to adjust its doctrine in light of changes in geopolitical realities. While the conventional army of the USSR and Warsaw Pact was massive enough that Soviet planners expected to never lose a conventional war in Europe, today several former Soviet republics are NATO members. The USSR could count on forces drawn from Ukraine for any war in Europe; in February Russia invaded Ukraine, an invasion that has struggled against massive resistance. 

The end of the Cold War, and the collapse of the Soviet Union, changed the balance of conventional power between Russia and Europe. Both the United States and Russia continued to reduce their nuclear stockpiles, but many weapons persist. Russia maintains roughly 1,600 warheads paired to missiles or planes that can reach the U.S., while the U.S. maintains 1,650 warheads that can reach Russia, and 100 tactical nuclear bombs stationed in Europe.

In addition, Russia maintains an estimated arsenal of 1,912 nonstrategic nuclear weapons. Writers in the U.S. have theorized that such weapons may be used in battle as part of a bid to force a negotiated end to the war in Ukraine, though nothing observed in modern Russian military doctrine suggests this is the case.

Instead, tactical nuclear weapons remain in the arsenals of the U.S. and Russia, an inherited legacy of intricately planning all the stages of the kind of war that should never be fought.

For other stories in the series, navigate here.