The Chevaline Re-entry Body (ReB) was the Re-entry vehicle (RV), of the British Chevaline warhead development of the Royal Navy's UGM-27 Polaris missile system. Chevaline was devised as an answer to the improved Soviet defences around Moscow, the system being intended to increase the probability of at least one warhead penetrating the city's Anti-ballistic missile (ABM) defences, something which the Royal Navy's earlier Polaris RVs were thought to be unlikely to do. The Chevaline system was in service from 1982 to 1996, when it was replaced by Trident D5.