This Day in History for October 20

Liz Truss steps down as British Prime Minister and leader of the Conservative Party amid the country's political crisis, serving for the least time of any British Prime Minister (49 days).

Syrian civil war: The Syrian Democratic Forces (SDF) declare victory in the Raqqa campaign.

Libyan Crisis: Rebel forces capture Libyan dictator Muammar Gaddafi and his son Mutassim in his hometown of Sirte and kill them shortly thereafter, ending the first Libyan civil war.

The general conference of the United Nations Educational, Scientific and Cultural Organization (UNESCO) passes the Convention on the Protection and Promotion of the Diversity of Cultural Expressions.

The Sloan Great Wall, once the largest cosmic structures known to humanity, is discovered by students at Princeton University.