Casus Belli
- Mysterious explosion on the battleship USS Maine (Spanish-American War)
- Pearl Harbor, Dec. 7, 1941 (World War II)
- Assassination of Archduke Franz Ferdinand (World War I)
- The Siege of Saguntum (Second Punic War)
- Attack on Fort Sumter (American Civil War)
- Invasion of Poland, Sept. 1, 1939 (World War II)
- The Egyptian blockade of the Straits of Tiran (The Six Day War)
- Gulf of Tonkin Incident (Vietnam War)
- War of Jenkins’ Ear, 1739 (Capt. Robert Jenkins’s loss of, well, you know)
- Britain’s forced conscription of Americans to fight Napoleon (War of 1812)
- Argentina’s invasion of Falkland/Malvinas Islands, 1982 (Falklands War)
- The Ems Telegram, 1870 (Franco-Prussian War)
- The British Army’s attempt to arrest Patriot leaders and seize arms outside Boston, 1775 (American Revolution)
More complicated than that, but that was the spark that started armed hostilities.
Next category:
Notable diplomats
- Benjamin Franklin, US minister to the French royal court (American Revolution)