- 1791 – The Polish Constitution of May 3, one of the earliest codified national constitutions in the world, was adopted by the Sejm.
- 1808 – Finnish War: Sweden lost the fortress of Suomenlinna to Russia.
- 1815 – Austrian troops led by Frederick Bianchi, Duke of Casalanza (pictured) defeated the forces under King Joachim Murat of Naples at the Battle of Tolentino, the decisive battle of the Neapolitan War.
- 1945 – World War II: German ocean liner Cap Arcona, left to float defencelessly in the Bay of Lübeck with thousands of prisoners from various concentration camps on board, was attacked and sunk by RAF Typhoons.
- 1947 – A new Constitution of Japan went into effect, providing for a parliamentary system of government, guaranteeing certain fundamental rights, and relegating the Japanese monarchy to a purely ceremonial role.
