US is preparing its first nuclear test in 33 years — here’s why it stopped, and what restarting means

In a move that could reshape global nuclear politics, US President Donald Trump on Thursday ordered the country's military to immediately resume nuclear weapons testing after a 33-year gap, minutes before meeting Chinese President Xi Jinping.

The decision signals the end of an era of restraint that began after the Cold War — and raises questions about why the US stopped testing in the first place, and why it’s starting again now.

How the nuclear age began

The nuclear era began in July 1945, when the United States detonated a 20-kiloton atomic bomb at Alamogordo, New Mexico — the world’s first nuclear test.


Within weeks, atomic bombs were dropped on Hiroshima and Nagasaki, ending World War II.

The Soviet Union followed in 1949, shattering America’s monopoly on nuclear weapons. What followed was a five-decade race of escalating tests and weapon development.

Between 1945 and 1996, more than 2,000 nuclear tests were carried out worldwide, according to the United Nations — 1,032 by the United States and 715 by the Soviet Union. Britain conducted 45, France 210, and China 45.

After the Comprehensive Nuclear Test-Ban Treaty (CTBT) was adopted in 1996, testing nearly came to a halt.

Since then, only 10 known tests have been conducted — two each by India and Pakistan in 1998, and six by North Korea between 2006 and 2017. The U.S. last tested in 1992, the Soviet Union in 1990, and China and France in 1996.

Why nuclear testing stopped

The global push to end nuclear testing stemmed from mounting evidence of environmental and human harm. Above-ground, underground, and underwater tests left vast areas contaminated and generations of people exposed to radiation.

In the Pacific and in Kazakhstan, entire communities were displaced or sickened by fallout from nuclear blasts. Environmental groups estimate that millions of people suffered long-term health consequences from decades of testing.

Diplomatically, the end of testing was seen as a way to cool Cold War tensions. The 1996 CTBT banned all nuclear explosions, “by everyone, everywhere.” Russia ratified the treaty in 2000; the U.S. signed it but never ratified.

In 2023, Russian President Vladimir Putin withdrew Russia’s ratification, arguing that Moscow should mirror Washington’s stance. The move deepened global concern that the treaty — already fragile — was losing its hold.

Why restart testing now?

Testing can serve two purposes: to gather data, or to send a geopolitical signal.

Nuclear scientists use tests to verify the performance of new weapons and to ensure old ones still function. But a live detonation — especially after decades of restraint — is also a powerful message.

In 2020, The Washington Post reported that Trump administration officials had privately debated whether to conduct a test as a show of strength toward Russia and China. Today’s order appears to have brought that idea to life.

Putin has warned repeatedly that if the U.S. resumes nuclear testing, Russia would follow suit. He has also said that “a global nuclear arms race is already underway.”

Who holds the world’s nuclear weapons?

Exact figures remain classified, but estimates from the Federation of American Scientists suggest that Russia possesses about 5,459 warheads and the U.S. around 5,177. The Washington-based Arms Control Association places the figures at 5,580 for Russia and 5,225 for the U.S.

At the height of the Cold War in 1986, global stockpiles exceeded 70,000 warheads. That number has since fallen to around 12,000 — still overwhelmingly concentrated in the hands of Moscow and Washington.

China is the third-largest nuclear power with around 600 warheads, followed by France (290), the United Kingdom (225), India (180), Pakistan (170), Israel (90), and North Korea (50).

All three major powers — the U.S., Russia, and China — are now modernising their nuclear arsenals, developing faster delivery systems and more advanced warheads.

If Washington follows through, the world could see the first U.S. nuclear detonation since 1992 — an event that would mark a dramatic reversal of decades of global restraint.

For nuclear powers, testing is about precision and deterrence. But for much of the world, it represents something more ominous: a return to the dangerous brinkmanship that defined the Cold War.

(With inputs from Reuters)