The Cold War may be over, but our stalemate on nuclear testing must remain strong  

The Pentagon is currently in the throes of a generational modernization program for the U.S. nuclear triad — comprising air, sea and land-based nuclear strike capabilities — that could cost taxpayers an estimated $1 trillion over 30 years.  

The effort is vast. It includes the introduction of a new strategic bomber, a new ballistic missile submarine and a new intercontinental ballistic missile (ICBM) system. While the B-21 Raider, the newest element of the triad’s air leg, has proven itself a rare example of a cost-effective defense procurement, the modernization program’s sea and land legs haven’t been so fortunate. Progress on the Navy’s new ballistic missile submarine, the Columbia class, has been disrupted by an inadequate defense industrial base, while the upcoming LGM-35 Sentinel ICBM was recently scandalized by the disclosure of fresh cost overruns.  

But there’s one worrying dimension of the U.S. modernization effort that has failed to get sufficient attention — the new W93 nuclear warhead and its implications for the future of nuclear testing. 

The W93 marks a significant moment in the history of the U.S. nuclear weapons program. It will be the first American nuclear warhead developed in the decades since the signing of the Comprehensive Test Ban Treaty (CTBT) in 1996, which banned all nuclear test detonations of any kind. While the CTBT has never formally entered force, it has had the effect of introducing a global taboo on nuclear testing, one that has commanded the respect of the great powers since the end of the Cold War.  

The last U.S. nuclear test (conducted underground) was carried out in 1992. Since 1998, the only nation to have conducted any kind of nuclear detonation is North Korea, infamously a flouter of an otherwise universal norm against testing. 

However, that was then. In today’s world of heightened tensions and renewed great power politics, the testing taboo is eroding at an alarming pace, with former President Trump’s national security adviser recently calling for a resumption of nuclear tests.  

Right now, none of the three great nuclear powers — the U.S., Russia and China — want to be the first to pull the trigger and break the taboo. But what would compel any of them to do so? The answer is nuclear modernization. 

All three powers are undergoing seismic changes to their respective nuclear weapons programs. China is pursuing a substantial buildup and may double its inventory by 2030. Russia is wrapping up a yearslong modernization effort of its own, one that has seen nuclear weapons play a much more prominent role in Moscow’s national security policy. And then there’s the U.S. Navy’s W93 warhead. 

The W93, still under development, is slated to replace older W76 and W88 warheads currently used on the Navy’s Trident II D5 submarine-launched ballistic missile. As the first warhead to be developed in the post-testing era, the question has arisen over whether the U.S. can credibly produce and field a reliable thermonuclear warhead without ever testing it first. 

The question isn’t unfounded. The quality of the existing U.S. stockpile, which dates back to the latter half of the Cold War, is something of an unknown. Meanwhile, institutional knowledge about sustainment, maintenance and production has atrophied in recent years. To correct this, the U.S. has even taken to resuming the production of plutonium pits — the core of a thermonuclear warhead — just to retain a baseline familiarity with the processes involved. 

The W93 adds to this quandary. The tricky work of designing a new warhead will face pressure to endure the rigorous testing that any other weapons system in the U.S. arsenal would, perhaps even more so since credibility and reliability are at the heart of nuclear deterrence. Despite this, the National Nuclear Security Administration confidently asserts that the new warhead “will not require additional nuclear testing to certify.”  

One way it has sought to get around this question is by basing many of its key components on older warheads that have been tested, though the extent to which the W93 is an update of a legacy system versus a totally new design is undisclosed. 

Another interesting opportunity has arisen to supplant yield testing with simulations at the National Ignition Facility, though this has not given experts ironclad confidence that tests won’t be deemed necessary someday. 

External pressures to test are also mounting, with China and Russia revamping old nuclear test sites and the latter also withdrawing its ratification of the CTBT last year. Though the Kremlin said it would respect the testing taboo as long as the U.S. does, it’s clear that the first to test could heighten tensions and invite other countries to conduct tests of their own.  

Washington should resist the pressures of this “testing cold war” and hold firm in its confidence in its deterrent. If nuclear testing is to make a comeback, the U.S. shouldn’t be the instigator. 

Scott Strgacich is a research associate at Defense Priorities.