Eisenhower, now US president, on 22 August 1958 announced a moratorium on nuclear testing. This did not mean an immediate end to testing; on the contrary, the United States, the Soviet Union and the United Kingdom all rushed to perform as much testing as possible before the deadline. A new British test series, known as Grapple Z, commenced on 22 August. It explored new technologies such as the use of external neutron initiators, which had first been tried out with Orange Herald. Core boosting using tritium and external boosting with layers of lithium deuteride were successfully tested, allowing a smaller, lighter two-stage devices. The international moratorium commenced on 31 October 1958, and Britain ceased atmospheric testing for good.