5. The Falklands War (1982)
In April 1982, Argentina invaded the Falkland Islands, a British overseas territory, without a formal declaration of war. The United Kingdom responded by dispatching a naval task force to reclaim the islands. The ensuing conflict lasted 74 days, resulting in 649 Argentine and 255 British military fatalities. The war concluded with the British regaining control over the islands (britannica.com).
