536: Byzantine General Belisarius enters Rome while the Ostrogothic garrison peacefully leaves the city, returning the old capital to its empire.

1212: Frederick II (later also Holy Roman Emperor) crowned King of Germany in Mainz.

1968: Douglas Engelbart demonstrates in “The Mother of All Demos” the computer system NLS (oN-Line System) to a live audience in San Francisco. Shows for the first time, the mouse, word processing, windows, hypertext links, video conferencing, real-time collaboration, and other modern computing concepts.

1990: Lech Wałęsa wins the first direct presidential election in Poland.

1992: US Marines and allied nations launch an amphibious and airborne operation in Mogadishu, Somalia to restore order to the war-torn nation. Authorized by UN Security Council Resolution 794 passed on December 3.

Source: Onthisday.com