Most countries stopped testing nuclear weapons after they signed the global Comprehensive Nuclear-Test-Ban Treaty (CTBT) starting from 1996. The treaty emerged amid growing concerns about human health and the environment above the ground, underground and underwater, from nuclear pollution.

The US conducted its first nuclear test in 1945. In all, the US has conducted 1,032 nuclear tests, according to the United Nations. The US last tested nuclear weapons in 1992. It signed the CTBT in 1996 but never ratified it.

The Soviet Union conducted 715 nuclear tests, the last of them in 1990. Since the USSR’s dissolution in 1990, Russia – which inherited the former superpower’s nuclear arsenal – has not conducted any nuclear tests. In 1996, Russia signed the CTBT, ratifying it in 2000. But Putin revoked Russia’s ratification of the treaty in 2023.

China last tested nuclear weapons in 1996. //

France last tested nuclear weapons in 1996. It conducted 210 tests between 1945 and 1996.

The United Kingdom conducted 45 nuclear tests from 1952, with the last one conducted in 1991.

Since the CTBT came into effect, 10 nuclear tests have taken place.

In 1998, India and Pakistan conducted two nuclear tests each. India and Pakistan have never signed the CTBT.

According to the UN, North Korea has conducted nuclear tests in 2006, 2009, 2013, 2016 and 2017. It conducted two tests in 2016. North Korea has also not signed the CTBT.

Nine states have nuclear arms, including the US, Russia, the UK, France, China, India, Pakistan, North Korea and Israel.

For decades, Israel has maintained nuclear ambiguity, also known as “opacity”. It has never publicly confirmed or denied the presence of its nuclear weapons programme.