In mid-April, US scientists announced that a test had recently and successfully been carried out on the B61-12 gravity bomb, a highly accurate, variable-yield replacement for the B61 nuclear bomb which has been a major part of America’s nuclear weapons arsenal since the late 1960s.

The B61-12 is said to be accurate to 30 meters, and its lowest yield settings give it a crater radius not much larger than that. Such bombs, officials say, could be set to lower yields while still destroying their intended target, lowering damage to the surrounding area, and limiting radioactive fallout. The first batch are planned to be finished by 2020.

While this pricey project is just a small fraction of a nuclear modernization scheme that will likely cost well over a trillion dollars before all is said and done, it is potentially the most dangerous, as the smaller usable yields make them substantially more usable for the US military, and risk the Pentagon believing they have the option to use “just a little nuke” here and there during warfare.

Today, a unilateral nuclear first strike would be considered an unthinkable action, turning the attacker into a global pariah overnight. Yet we have seen time and again that the bar for behavior in war is a rapidly drifting line, particularly in this era of constant US warfare.

The use of drones in warfare is a good example. In 2001 the United States conducted the first ever drone strike in Afghanistan, firing a Hellfire missile at a vehicle convoy. Just over two years later, the US carried out its first strike in a nation that they weren’t at war in, Pakistan. By President Obama’s early years, drone strikes in Pakistan had become commonplace, and by 2011, less than a decade after its first use, the US used a drone in Yemen to assassinate a US-born American citizen, Anwar Awlaki.

The first time deployment for any significant new weapon is always a big deal. This was seen on April 13, when for the first time ever the US dropped the GBU-43/B MOAB, also called the “Mother of All Bombs.” The largest non-nuclear bomb ever used, this was dropped in Afghanistan, nominally to target ISIS, but with US officials mostly emphasizing the “message” its use sent to other nations the US is hostile toward.

And so it doubtless would be for the B61-12. The first use of a low-yield version of the nuclear bomb would be a media event, though judging from the cable news reaction to the MOAB, it would likely be presented mainly as an interesting event, and one which underscores the current president’s willingness to bring America’s military might to bear.

While the size of the effected region for a low-yield nuclear strike could be very limited indeed with the new bomb, even on its low settings the B61-12 is more than a factor of 1,000 more powerful than the MOAB. To make matters worse, the precedent of a low-yield bomb would doubtless carry over into higher and higher settings.

Indeed, it isn’t hard to suppose that while the first nuclear strike would be a media curiosity, the second strike would be dramatically less so, and with a few more deployments into a few different military theaters, of which the US is never short, low-yield nuclear strikes could easily become as routine as US drone strikes assassinating unnamed “suspects” overseas.

Obviously, I’m not the first person that has thought of this, nor is the Air Force blind to the potential of having nuclear weapons with a much lower usage threshold. Terrifyingly enough, the Air Force has presented this as a major selling point for the B61-12.

Former Air Force Chief of Staff Norton Schwartz argued that this practical usability would greatly increase the deterrent impact of the bomb to America’s nuclear arsenal, since other nations would believe the US would be more likely to use such accurate bombs in minor engagements.

Unspoken in this is that they would be correct in believing so. While America’s extent nuclear stockpile is virtually unusable in anything short of a civilization-ending nuclear exchange, and it would be unfathomable to imagine the US dropping any of its current nuclear weapons in Afghanistan, Libya, or Yemen, officials would doubtless argue that a “special case” use of a 50 kiloton bomb on a fortification could be easily justified.

As with drone strikes, the first time is the hardest to sell, and the special case becomes less special each time, to the point that casual nuclear strikes could, and likely rapidly would, become routine, bringing nuclear warfare into the world in a way that the Cold War never could.

The danger of this is palpable, as once strikes nuclear strikes start happening, there is no stopping them, and the trend will everywhere and always be bigger bombs and lower barriers to usage. Every proxy war would be likely to “go nuclear” in short order, and quickly escalate out of control.

The solution to this is a straightforward one – the United States must make a declaration of no first use of nuclear weapons. Such a declaration would have ample precedent: both China and India have pledged no first use, and the Soviet Union made a similar pledge.

As recently as last year, President Obama was discussing making a similar declaration on behalf of the United States, but military officials and cabinet hawks shouted him down, arguing that a pledge of no US nuclear first strikes would harm America’s military credibility.

The argument scared Obama away from the declaration, but was of course nonsense. A nuclear first strike is not an expression of a nation’s military credibility, but rather is an act of either desperation or lawless, naked aggression.

As the world’s leading nuclear power, a US no-first-use pledge would go a long way toward convincing other nations to follow suit, and would commit America’s credibility to not going down the path of reckless nuclear aggression, providing at least some assurance that US governments would not take advantage of the B61-12 to conduct small nuclear first strikes against non-nuclear states or random insurgencies.

Jason Ditz is news editor at Antiwar.com, a nonprofit organization dedicated to the cause of non-interventionism. His work has appeared in Forbes, Toronto Star, Minneapolis Star-Tribune, Providence Journal, Washington Times and Detroit Free Press.