Wikipedia:Today's featured article/November 10, 2021

Operation Grapple was a series of British nuclear weapons tests carried out in 1957 and 1958 at Malden Island and Christmas Island in what is now Kiribati. Britain had successfully tested an atomic bomb in October 1952, and in July 1954, decided to develop a hydrogen bomb. In the first test, Grapple 1 (pictured), the bomb's yield was below its designed capability. The second, Grapple 2, was the largest ever achieved by a single-stage device. The third, Grapple 3, also had a low yield. A further test, Grapple X, exceeded expectations. Grapple Y, in April 1958, yielded about three megatonnes and remains the most powerful British nuclear weapon ever tested. Much of its yield came from its thermonuclear reaction, making it a true hydrogen bomb, and the United Kingdom became the third nation to possess one. A final series of four tests, Grapple Z, tested techniques for making bombs immune to predetonation by nearby nuclear explosions.