BIKINI state

The BIKINI state was an alert state indicator previously used by the UK Ministry of Defence to warn of non-specific forms of threat, including civil disorder, terrorism or war. Signs giving the current alert state were displayed at the entrance to government buildings and military installations. It was established on 19 May 1970. According to the Ministry of Defence, the word bikini was randomly selected by a computer.

Whilst similar to the DEFCON alert states used in the United States, the BIKINI levels were defined by the section of the military or organisation rather than UK-wide, and as a result, countermeasures and reactions to differing states may differ as acutely as from building to building. The highest levels of alert, RED and AMBER, were only intended to be maintained for limited times. The WHITE state has never been used in the history of the system.

The system was illustrated in the British television drama Threads, produced by the BBC in 1984.

Gareth Parry reported a British ship going to "Red Alert" during an Argentinian air raid on May 25, 1982.

It was replaced by a more general and public terrorism alert status, UK Threat Levels, an alert state system in use by the British government since 1 August 2006.

NATO military alert state
In addition to Bikini alerts that applied to individual installation NATO had a "Counter-Surprise" Military Alert System to mobilise its military forces.