404 BC – Peloponnesian War: Lysander's Spartan Armies defeated the Athenians and the war ends.
1792 – Highwayman Nicolas J. Pelletier becomes the first person executed by guillotine.
1915 – World War I: The Battle of Gallipoli begins—The invasion of the Turkish Gallipoli Peninsula by Australian, British, French and New Zealand troops begins with landings at Anzac Cove and Cape Helles.
1916 – Easter Rebellion: The United Kingdom declares martial law in Ireland.
1916 – Anzac Day is commemorated for the first time on the first anniversary of the landing at Anzac Cove.
1939 – DC Comics publishes its second major superhero in Detective Comics #27; he is Batman, one of the most popular comic book superheroes of all time.
1953 – Francis Crick and James D. Watson publish "Molecular Structure of Nucleic Acids: A Structure for Deoxyribose Nucleic Acid" describing the double helix structure of DNA.
1965 – Teenage sniper Michael Andrew Clark kills three and wounds six others shooting from a hilltop along Highway 101 just south of Santa Maria, California.
1966 – The city of Tashkent is destroyed by a huge earthquake.
1972 – Vietnam War: Nguyen Hue Offensive – The North Vietnamese 320th Division forces 5,000 South Vietnamese troops to retreat and traps about 2,500 others northwest of Kontum.
1974 – Carnation Revolution: A leftist military coup in Portugal overthrows the fascist Estado Novo regime and establishes a democratic government.
1975 – As North Vietnamese forces close in on the South Vietnamese capital Saigon, the Australian Embassy is closed and evacuated, almost ten years to the day since the first Australian troop commitment to South Vietnam.
1981 – More than 100 workers are exposed to radiation during repairs of a nuclear power plant in Tsuruga, Japan.
2003 – The Human Genome Project comes to an end two and a half years earlier than expected.
2005 – The final piece of the Obelisk of Axum is returned to Ethiopia after being stolen by the invading Italian army in 1937.
2011 – At least 300 people killed in deadliest tornado outbreak in the Southern United States since the 1974 Super Outbreak.