Continuity of government (COG) is the principle of establishing defined procedures that allow a government to continue its essential operations in case of a catastrophic event such as nuclear war. COG was developed by the British government before and during World War II to counter threats, such as that of the Luftwaffe bombing during the Battle of Britain. The need for continuity of government plans gained new urgency with nuclear proliferation. In the US, COG is no longer limited to nuclear emergencies; the Continuity of Operations Plan was activated following the September 11 attacks.