1054

By place

Byzantine Empire

• Sultan Tughril leads a large Seljuk army out of Azerbaijan into Armenia, possibly to consolidate his frontier, while providing an incentive to his Turkoman allies in the form of plunder. Tughril divides his army into four columns, ordering three to veer off to the north to raid into central and northern Armenia, while he takes the fourth column towards Lake Van. The Seljuk Turks capture and sack the fortress city of Artchesh, after an 8-day siege.

  Europe

• Battle of Mortemer: The Normans, led by Duke William the Bastard, defeat a French army, as it is caught pillaging and plundering. King Henry I of France withdraws his main army from Normandy as a result. Guy I, count of Ponthieu, is captured during the course of the battle.

  Scotland

• July 27 - Siward, earl of Northumbria, invades Scotland, to support King Malcolm III against Macbeth, who has usurped the Scottish throne from Malcolm's father, Duncan I. Macbeth is defeated at Dunsinane.

  Africa

• The Almoravids retake the trading center of Aoudaghost from the Ghana Empire. Repeated Almoravid incursions, aimed at seizing control of the trans-Saharan gold trade, disrupt Ghana's dominance of the trade routes.

  Asia

• Lý Nhật Tôn, third king of the Lý Dynasty, begins to rule in Vietnam, and changes the country's official name to Đại Việt.

  By topic

Astronomy

• July 4 - SN 1054, a supernova, is first observed by the Chinese, Arabs and possibly Native Americans, near the star Zeta Tauri. For 23 days it remains bright enough to be seen in daylight. Its remnants form the Crab Nebula.

  Religion

• Spring - Pope Leo IX sends a legatine mission, under Cardinal Humbert of Silva Candida, to Constantinople, to negotiate with Patriarch Michael I Cerularius, in response to his actions concerning the church in Constantinople.
• July 16 - Humbert of Silva Candida, representative of the newly deceased Leo IX, breaks the relations between Western and Eastern Churches, through the act of placing an invalidly-issued Papal Bull of excommunication during the celebration of the Divine Liturgy.