An alert state or state of alert is an indication of the state of readiness of the armed forces for military action or a state against natural disasters, terrorism or military attack. The term frequently used is "on high alert". Examples scales indicating alert state are the DEFCON levels of the US military, South Korea's "Jindogae" system, and the UK Threat Levels. High alert states are synonymous with "red alert".
- U.S. Military on 'High Alert' [Retrieved 2013 April 12]
- R. van Dijk Encyclopedia of the Cold War, Volume 1
- "NK fires shells onto S. Korean island, kills 2 Marines". Dong-A Ilbo. 24 November 2010. Retrieved 30 November 2010.
- Home Office Terrorism and national emergencies [Retrieved 2013 April 12] Archived 29 July 2013 at the Wayback Machine
- The dictionary definition of red alert at Wiktionary