North Korea conducted its fourth nuclear detonation on 6 January, 2016. North Korean media made announcements that the regime had successfully tested a hydrogen bomb. However third-party experts—as well as officials and agencies in South Korea—doubted North Korea’s claims and contend that the device was more likely to have been a fission bomb such as a boosted fission weapon. Such weapons use hydrogen fusion to produce smaller, lighter warheads suitable for arming a delivery device such as a missile, rather than to attain the destructive power of a true hydrogen bomb.