Allied Command Europe was established under General of the Army Dwight D. Eisenhower, U.S. The exercise was jointly commanded by Supreme Allied Commander Atlantic Admiral Lynde D. McCormick, United States Navy, and Supreme Allied Commander Europe General Matthew B. Ridgeway, U.S. The United States, the United Kingdom, Canada, France, Denmark, Norway, Portugal, Netherlands, and Belgium participated. The Western Union Defence Organization had previously carried out Exercise Verity, a 1949 multilateral exercise involving naval air strikes and submarine attacks. Exercise Mainbrace brought together 200 ships and over 50,000 personnel to practice the defense of Denmark and Norway from the Soviet attack in 1952. It was the first major NATO exercise.
Its primary goal was “to impose upon Russia the will of the United States and the British Empire”. Although the scenario made use of nuclear weapons, they were not expected to play a decisive role. The plan was rejected by the British Chiefs of Staff Committee as militarily unfeasible. Operation Dropshot was the 1950s United States contingency plan for a possible nuclear and conventional war with the Soviet Union in the Western European and Asian theaters.
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Carnegie Council for Ethics in International Affairs. Jonathan Walker (2013). Operation Unthinkable: The Third World War. The History Press. p. Department of History, Northeastern University. Is this the start of World War III? Naval War College. Press, Naval War College. Caffrey, Matthew B. (2019). On wargaming: how wargames have shaped history. How they may shape the future. Newport, Rhode Island: Naval War College Press. British War Cabinet; Joint Planning Staff; Public Record Office (11 August 1945). “Operation Unthinkable: ‘Russia: Threat to Western Civilization'”. Center for Naval Warfare Studies.
Karmanau, Yuras; Heintz, Jim; Isachenkov, Vladimir; Litvinova, Dasha (24 February 2022). “Russia presses invasion to outskirts of Ukrainian capital”. Faith, Ryan (11 March 2022). “Ukraine Isn’t World War III. It’s Not Even Close”. Elliott, Larry (24 May 2022). “Ukraine invasion maybe start of ‘third world war‘, says George Soros”. Europe since World War II. Kyiv: American Broadcasting Company. Skomaskanda, Honderich; Sumi, Holly (18 April 2024). “Ukraine warns of WW3 ahead of long-stalled Congress aid vote”. Herszenhorn, David M. (4 March 2022). “The fighting is in Ukraine, but risk of World War III is real”. Haynes, Deborah (6 March 2022). “Ukraine invasion: Has World War Three already started? Some security experts believe existential global conflict has begun”. ABC News. Photograph by Evgeniy Maloletka (AP Photo).
The Turks claimed that the aircraft violated Turkish airspace, a claim denied by the Russians; the plane was in the region as part of the Russian military intervention in the Syrian civil war, in which Turkey supported opposing forces. The incident led to numerous media and individuals commenting that it could have sparked and escalated into a world war. This marked a major escalation in the Middle Eastern crisis and in what had been a decades-long proxy conflict between Iran and Israel. On 13 June 2025, Israel’s military launched a series of missile strikes against Iran targeting its nuclear and military infrastructure. US negotiations with Iran collapsed.