Operation Grapple, and operations Grapple X, Grapple Y and Grapple Z, were the names of British nuclear weapons tests of very-early hydrogen bombs. These tests were carried out from 1956 until 1958 at Malden Island and Christmas Island in the Central Pacific Ocean. Nine nuclear explosions were executed during these series of nuclear weapon tests, culminating in the United Kingdom's becoming the third recognized possessor of thermonuclear weapons. The Orange Herald was a large fission bomb which was hoped to arm a future ballistic missile. The bomb was dropped and detonated by a Valiant bomber on May 31, 1957. It exploded with a force of about 720 kilotons. The yield was the largest ever achieved by similar bomb designs. This bomb was hailed by the government as a new type of hydrogen bomb and the fact that it was a fission bomb was kept secret by the government until the end of the Cold War. A 400 kiloton very-large atomic bomb code-named "Green Grass" was derived from Orange Herald, and it was deployed during the period before an actual H-bomb became available.
