The simplest method for determining the effectiveness and other properties of a given nuclear weapons design is to conduct a test session. In some countries, modern supercomputers can accurately model nuclear explosions, reducing the need for actual tests. Since 1945, when the world’s first atomic bomb was detonated at the Trinity site in New Mexico, nuclear weapons testing has taken place. The Limited Test Ban Treaty, signed in 1963 to slow the nuclear arms race and prevent the release of harmful nuclear fallout into the atmosphere, prohibited signatories from testing nuclear weapons in the atmosphere, on the ground, or in the water. Although non-signatories India and Pakistan tested nuclear weapons in 1998, the Comprehensive Test Ban Treaty forbade all forms of nuclear testing among its signatories in 1996. In 2006, North Korea conducted a nuclear test, which enraged the international community.
Between 1945 and 1992, the United States tested over 1,000 nuclear bombs, making it the world’s leading nuclear weapons tester. The yields for these tests ranged from a ton of TNT to 15 megatons for the Bravo test. Using the Threshold Test Ban Treaty, the US and the USSR limited the maximum yield of underground tests to 150 kilotons in 1976. The Nevada Test Site, near Las Vegas, was used for earlier tests of smaller yields, and the Pacific Proving Grounds in the Marshall Islands was used for larger tests. Despite the fact that the Nevada Test Site exploded over 925 bombs, accounting for 75% of all testing, the total yield of all US tests is only about 15%. The 125 bombs that exploded at the Pacific Proving Grounds accounted for roughly 80% of the total yield.
Soldiers and observers were only a few miles away from the test sites in previous tests. To protect the surrounding population, increased yields for future explosions necessitated greater distances from the detonation point or underground tests. The Tsar Bomba, a 50 megaton nuclear test that could cause third-degree burns from 62 miles (100 kilometers) away, was carried out by the Soviets. Nukes with a yield of 5 megatons or more have been found to be capable of destroying large swaths of a major city. Because the United States prioritized accuracy over yield, their bombs were typically smaller than Soviet variants, which were designed to cause damage even when accuracy was low.