A multiple independently targetable reentry vehicle (MIRV) is a ballistic missile payload containing several warheads, each capable of being aimed to hit one of a group of targets. By contrast a unitary warhead is a single warhead on a single missile. An intermediate case is the multiple reentry vehicle (MRV) missile which carries several warheads which are dispersed but not individually aimed. Only the United States (1970), Russia (1975), Britain (1979), France (1985), China (2007) are known to have developed MIRV missiles.