August 20

Wednesday 20, 1986:

In Edmond, Oklahoma, US Postal employee Patrick Henry Sherrill guns down 14 of his co-workers and then commits suicide.

Friday 20, 1982:

Lebanese Civil War: A multinational force lands in Beirut to oversee the PLO withdrawal from Lebanon.

Wednesday 20, 1975:

Viking program: NASA launches the Viking 1 planetary probe toward Mars.

Monday 20, 1900:

Japan's primary school law is amended to provide for four years of mandatory schooling.

Saturday 20, 636:

Battle of Yarmuk: Arab forces led by Khalid bin Walid take control of Syria and Palestine away from the Byzantine Empire, marking the first great wave of Muslim conquests and the rapid advance of Islam outside Arabia.