WASHINGTON – President Donald Trump’s new nuclear strategy emphasizes a strategic shift towards the use of “low-yield” nuclear weapons to increase deterrence against mounting nuclear threats from Russia, China, and North Korea.

Experts have questioned this decision, saying that the term “low-yield” is a deceptive description of these nuclear weapons. Moreover, they say, a strategy that depends on the possible use of smaller bombs could enhance the chance that a nuclear weapon will be used.

Alexandra Bell, a director of policy with the Center for Arms Control and Non-Proliferation, stressed that talking about low-yield nuclear weapons as if they are “small” can be dangerous.

“Coming down to low-yield is coming back to the kind of weapons that were used in World War II,” Bell said. “These things aren’t little…It concerns me that they talk about them like they are not a big deal.”

Here are answers to three important questions about these so-called low-yield nuclear weapons:

1. How destructive is a “low-yield” nuclear bomb?

Experts said that the most important thing to remember when talking about nuclear weapons, whether low-yield or large-yield, is understanding how big any of these weapons actually are.

A nuclear bomb is measured in terms of its explosive yield, which is referenced in terms of “tons,” “kilotons,” and “megatons” of the TNT explosive power they put off. For example, the explosive yield from a conventional bomb that is dropped by bombers would be about 500 pounds.

The largest conventional weapon in the U.S. arsenal is the “Mother of all Bombs,” or MOAB. The last time this bomb was dropped was in Afghanistan in 2017 by the Trump administration.

According to Joe Cirincione, the president of the Ploughshares Fund, a non-profit that funds organization and people working to eliminate nuclear weapons, the explosive yield from the MOAB is around 11 tons, about 44 times the size of a conventional bomb.

While low-yield nuclear bombs can range from .1 kilotons to 10, 20, or 50 kilotons, according to Cirincione, the explosive yield from a low-yield nuclear weapon is equivalent to 1,000 MOABs. That is equivalent to the sizes of bombs dropped by the U.S. over Nagasaki and Hiroshima at the end of World War II.

“When people talk low-yield, what they generally mean is something that is down like Hiroshima size,” Cirincione said. “That is… ‘only’ 10 thousand tons of explosive force or…1,000 MOABs.”

The atomic bomb dropped over Hiroshima was 15 kilotons and the one dropped over Nagasaki was around 20 kilotons.

2. How many low-yield nuclear weapons does the US have in its stockpile?

A 2017 report of the Bulletin of the Atomic Scientists estimated that the U.S. currently has a total inventory of about 6,780 nuclear weapons. However, a significant amount of these weapons is either “retired” or are being held in “reserve.”

The current active total stockpile of nuclear weapons is about 4,480 with 1,740 deployed.

According to Bell and Cirincione, about1,000 bombs in this stockpile are low-yield nuclear weapons. Around 150 are currently in Europe, Cirinicione said, while the rest have been pulled pack to the U.S.

Nearly half of this low-yield stockpile is in the form of “gravity bombs” or “airdrop” bombs called B-61s. Cirincione said these are not traditional low-yield weapons because they can be calibrated to a specific explosive yield ranging from .3 kilotons to 50 kilotons.

The U.S. also has a version of the B-61 on an air-launched cruise missile that is carried by B-52 bombers.

In the newly released Nuclear Posture Review, the Trump administration signaled it is developing a strategy in which low-yield nuclear war heads will be attached to ballistic missiles that could be launched by submarines and delivered thousands of miles away.

While the 2018 NPR says that there are no plans to increase the nuclear stockpile, this strategy in effect could increase the number of low-yield nuclear weapons. Cirincione said one possibility in fitting a low-yield warhead to a ballistic missile would involve the adaptation of Hydrogen bombs. Those bombs are built with two interrelated components: one creates an atomic explosion which in turn triggers a load of hydrogen fuel that greatly increases the magnitude of the explosion.

Ironically, the primary atomic explosion would be considered a low-yield warhead, although it is about 6.5 kilotons of explosive force.

3. What are the debates surrounding the use of low-yield weapons?

The main controversy is over whether access to more low-yield nuclear weapons would increase or decrease the likelihood that they would be used because they are considered to be a less powerful nuclear option.

Both Bell and Cirincione agree that more low-yield nuclear weapons enhance the chance they would be used. However, not all experts agree.

Matthew Costlow, a national defense analyst and nuclear deterrent expert at the National Institute for Public Policy, said that low-yield nuclear weapons have been part of nuclear arsenals for decades and yet one has never been used.

“Just because you have the capabilities to use a nuclear weapon does not mean it is any easier or harder to use,” Costlow said. “It is simply untrue and unsupported by historical evidence that lower-yield nuclear weapons increase the risk of use.”

Sharon Weiner, a political science professor at American University who specializes in national security and nuclear weapons, notes that in case of an attack, a country would not be able to tell what type of nuclear weapon was coming its way until it hit its target.

Because of this, she said, there is no way to be able to control escalation. Consequently, a low-yield strike could still escalate into a large-scale retaliatory nuclear attack.

An important thing to remember when talking about nuclear weapons is that, while they are measured by explosive force, the damage they cause is not simply limited to the explosion.

In a recent article in The Atlantic, atomic historian Alex Wellerstein said that a kiloton or megaton is simply a unit of energy. Nuclear weapons also result in massive amounts of heat and radiation causing damage to both people and the environment long after the initial explosion.