Wikipedia:Selected anniversaries/August 20
August 20: St. Stephen's Day in Hungary.
- 636 - Arab forces led by Khalid ibn al-Walid took control of Syria and Palestine in the Battle of Yarmouk, marking the first great wave of Muslim conquests and the rapid advance of Islam outside Arabia.
- 917 - Bulgarians led by Tsar Simeon I drove the Byzantines out of Thrace with a decisive victory in the Battle of Anchialus.
- 1882 - The "1812 Overture", an orchestral work by Pyotr Ilyich Tchaikovsky (pictured), was first performed at the Cathedral of Christ the Saviour in Moscow.
- 1968 - At least 200,000 Warsaw Pact troops and 5,000 tanks invaded Czechoslovakia, abruptly ending a period of political liberalization known as "Prague Spring".
- 1991 - Estonia regained its independence in the Singing Revolution, breaking away from the Soviet Union.