Thirty years ago, on September 24, 1996, the Comprehensive Nuclear Test Ban Treaty (CTBT) was opened for signature.  President Bill Clinton became the first to sign.  However, the treaty has never entered into force, in part because the Senate did not consent to its ratification.

Prospects for the CTBT ever entering into force appear dim.  That’s truly unfortunate.  Of the nuclear control treaties concluded over the past seven decades, none offered the United States such a one-sided advantage.

If in force, the CTBT would ban any nuclear test or explosion that produces a nuclear yield (the zero-yield standard). One hundred and eighty-seven countries have signed it, but 44 “Annex 2” countries, countries that have nuclear weapons or nuclear reactors, must ratify the treaty for it to take effect.  Nine of those 44 have not:  China, Egypt, India, Iran, Israel, North Korea, Pakistan and Russia in addition to the United States.  (India, Israel, North Korea and Pakistan also have yet to sign the treaty, while Russia ratified in 2000 but rescinded its ratification in 2024 because the United States had not ratified.)

The negotiators did not intend the CTBT to favor the United States.  The treaty’s prohibition on testing applies equally to all signatories.  However, the treaty would have the practical effect of preserving a U.S. nuclear knowledge advantage.

How?  The United States has conducted more nuclear explosive tests than the rest of the world combined.  Of 2056 total nuclear explosive tests, 1030 were American, and one could add 24 more tests if joint U.S.-British tests were taken into account. The Soviet Union conducted 715 tests, but Russia has conducted no nuclear explosive tests since the Soviet collapse in 1991.  China, commonly cited by the Pentagon as the pacing strategic challenge facing the United States, conducted 45 tests—less than 5 percent of the U.S. total.

Nearly 75 percent of the nuclear explosive tests were conducted underground.  In 1963, the United States, Soviet Union and Britain signed the Limited Test Ban Treaty. That treaty prohibited signatories from testing in the atmosphere, underwater or in outer space, forcing their testing programs to move underground.  Other countries followed suit, with China conducting the last aboveground test in 1980.

The United States learned more than others from underground testing, because it prepared tests that collected more data on the weapons’ performance and effects.  For example, vertical shafts for tests at what was then the Nevada Nuclear Test Site were typically drilled with a diameter of six to 12 feet, significantly larger than the nuclear devices being tested.  The large diameter was dictated by a desire to maximize area right above the nuclear device for instruments that would capture a range of data in the instant before they were vaporized.  By contrast, Soviet vertical shafts were smaller, about a meter (3.3 feet) in diameter, allowing considerably less space for instrumentation.  (Both sides also used horizontal shafts for tests.)

Despite the opportunity to lock in this knowledge advantage for the United States, Senate opponents of the treaty out-maneuvered the Clinton administration in 1999.  They brought the CTBT to a vote before administration officials made the case for the treaty and provided limited time for substantive Senate debate on its merits and possible flaws.  The vote fell well short of the 67 ayes needed for consent to ratification.

Concerns about the ability to maintain the U.S. nuclear stockpile without nuclear explosive testing and the possibility of adversary cheating were cited as key reasons for the failure to win ratification. Thirty years later, much has been done to address both concerns, though compliance questions have now arisen.

The Stockpile Stewardship Program employs advanced computers, exotic technologies and other means to assess U.S. nuclear weapons without the need for nuclear explosive testing.  For three decades, the directors of the Los Alamos, Sandia and Lawrence Livermore National Labs plus the commander of Strategic Command have made annual certifications that the U.S. nuclear arsenal is safe, secure and reliable with no technical reason to resume testing. 

Over the years, U.S. national technical means of verification as well as the CTBT Organization’s International Monitoring System have improved their abilities to detect nuclear tests.  However, in early 2026, the Trump administration asserted that China had conducted a nuclear explosive test in 2020, a claim the Chinese denied.  U.S. concerns regarding Russian testing that was inconsistent with the zero-yield standard date back to 2019.

Given the breakdown in bilateral arms control between Washington and Moscow, China’s rapid expansion of its nuclear arsenal, and the overall state of global relations, the CTBT likely will not enter into force, at least not any time soon.  That leaves an informal moratorium on nuclear testing, observed since 1998 by every country except North Korea (and China?).

Protecting the knowledge advantage and avoiding a return to unconstrained nuclear testing should remain U.S. goals.  It would hardly be in the U.S. interest, for example, if China were to test new, smaller warheads in order to put more on its strategic ballistic missiles.  Whether that can be done remains to be seen.  The CTBT increasingly looks like a missed opportunity.