What happened on September 20

Holy Roman Empress from 1046 to 1056

Agnes of Poitou was the queen of Germany from 1043 and empress of the Holy Roman Empire from 1046 until 1056 as the wife of Emperor Henry III. From 1056 to 1061, she ruled the Holy Roman Empire as regent during the minority of their son Henry IV.

1066 battle near York, England

The Battle of Fulford was fought on the outskirts of the village of Fulford, just south of York in England, on 20 September 1066. King Harald III of Norway, also known as Harald Hardrada, a claimant to the English throne, and Tostig Godwinson, his English ally, fought and defeated the Northern Earls Edwin and Morcar.

Founder of the Ayyubid dynasty (c. 1137–1193)

Salah ad-Din Yusuf ibn Ayyub, commonly known as Saladin, was a Kurdish commander and political leader. He was the founder of the Ayyubid dynasty and the first sultan of both Egypt and Syria. An important figure of the Third Crusade, he spearheaded the Muslim military effort against the Crusader states in the Levant.

13th-century revolts by Old Prussians against the Teutonic Knights

The Prussian uprisings were two major and three smaller uprisings by the Old Prussians, one of the Baltic tribes, against the Teutonic Knights that took place in the 13th century during the Prussian Crusade. The crusading military order, supported by the Popes and Christian Europe, sought to conquer and convert the pagan Prussians. In the first ten years of the crusade, five of the seven major Prussian clans fell under the control of the less numerous Teutonic Knights.

Antipope from 1378 to 1394

Robert of Geneva was elected to the papacy as Clement VII by the cardinals who opposed Pope Urban VI and was the first antipope residing in Avignon, France. His election led to the Western Schism.