Film footage of US nuclear tests in the country’s southwestern desert from the 1940s and 1950s has been restored, showing some of history’s most powerful weapons blasts in high definition.

Axar.az reports that, YouTuber atomcentral restored footage from the US Federal Civil Defense Administration records of two tests: the infamous 1945 Trinity blast, which inaugurated the nuclear era, and the 1953 Upshot-Knothole Grable test, the only exercise in which a nuclear device was detonated after being fired from an artillery piece.

Trinity was the world's first nuclear weapon to be detonated, tested by the US military in the Jornada del Muerto valley in New Mexico on July 16, 1945. The test was the culmination of the Manhattan Project, a top secret program by the US during World War II to build and test an atom bomb before Nazi Germany, from which many of the program's top scientists had come.

The test confirmed the basic functioning of a fission bomb. The website Trinity Remembered explains it:

"In an atomic explosion, a chain reaction picks up speed as atoms split, releasing neutrons plus great amounts of energy. The escaping neutrons strike and split more atoms, thus releasing still more neutrons and energy. In a nuclear explosion this all occurs in a millionth of a second, with billions of atoms being split."

The Trinity blast was equivalent to 22,000 tons of TNT exploding at once. Because it worked, the US shipped two bombs to the western Pacific, where they were dropped on the Japanese cities of Hiroshima and Nagasaki on August 6 and August 9, respectively, killing roughly 135,000 people and forcing an end to the war. The US is the only country to have used nuclear weapons in combat.