Year 1184 (MCLXXXIV) was a leap year starting on Sunday (link will display the full calendar) of the Julian calendar. Events By place Europe May 20 – Diet of Pentecost: Emperor Frederick I (Barbarossa) organises a conference in Mainz. During the diet Frederick negotiates with Henry the Lion about an anti-French alliance with England. June 15 – Battle of Fimreite: King Sverre of Norway defeats and kills his rival, Magnus V (Erlingsson) near Fimreite. Sverre takes the throne and becomes sole ruler of Norway (until 1202). Summer – Almohad forces reconquer the Alentejo (except for Évora), and besiege Lisbon on land and blockade the port with their navy. A Portuguese soldier manages to swim to the largest ship of the fleet and to sink it. This ship was so tall, it would have allowed the Muslims to easily reach the walls of the city. The next day, the Almohads have to retreat, taking with them a number of civilian captives. Siege of Santarém: Almohad forces under Caliph Abu Yaqub Yusuf march towards Badajoz and besiege Santarém, which is defended by King Afonso I (the Conqueror). Upon hearing of Abu Yusuf's attack, Ferdinand II of León marches his army to Santarém to support his father-in-law, Afonso. Abu Yusuf, in an attempt to break the siege, is wounded by a crossbow bolt and dies on July 29. October 29 – The 18-year-old Prince Henry, eldest surviving son of Frederick I, is engaged to Princess Constance, heiress to the Kingdom of Sicily, at Augsburg in the episcopal palace. The city of Abbeville receives its commercial charter by King Philip II (Augustus). England The first royal ordinance, demanding that the Knights Templar and Hospitaller assist in the collection of taxes, is promulgated. King Henry II encourages his youngest (and favorite) son John to seize Aquitaine from his brother Richard. May – A serious fire damages Glastonbury Abbey and destroys several buildings. Africa May – Berber forces under Ali Banu Ghaniya seize the Almohad cities of Algiers, Béjaïa and Constantine by surprise. While he is away from his base in Mallorca, one of his brothers, Muhammad, takes control of the island and calls in the Almohads, who intend to capture Mallorca for themselves. Banu Ghaniya arrives just in time, to defeat the Almohads and recapture the island. August 10 – Abu Yusuf Yaqub al-Mansur is proclaimed the new caliph of the Almohad Caliphate, after his