View source for 1091

=== By place ===

==== Byzantine Empire ====
* Spring &ndash; [[Tzachas]], a Seljuk Turkish military commander, establishes an independent maritime state centred in the [[Ionia]]n coastal city of [[Smyrna]] (modern-day [[İzmir]]). He proclaims himself emperor (''[[basileus]]''), and concludes an alliance with the [[Pechenegs]] in [[Thrace (theme)|Thrace]]. Tzachas uses his fleet to blockade [[Constantinople]] by sea, while the Pechenegs besiege the capital by land.<ref>Brian Todd Carey (2012). ''Road to Manzikert: Byzantine and Islamic Warfare (527–1071)'', p. 160. {{ISBN|978-1-84884-215-1}}.</ref>
* [[April 29]] &ndash; [[Battle of Levounion]]: Emperor [[Alexios I Komnenos|Alexios I]], supported by his allies, defeats 80,000 of Pechenegs (including women and children) at the [[Maritsa|Evros River]], near [[Enez|Enos]] (modern [[Turkey]]). The [[Cumans]] and Byzantine forces fall upon the enemy camp, slaughtering all in their path. The Pechenegs are butchered so savagely, that this people is almost wiped out.

==== Europe ====
* Spring &ndash; King [[Stephen II of Croatia|Stephen II]], the last member of the [[Trpimirović dynasty]], dies without leaving an heir after a 2-year reign. War and unrest breaks out in [[Kingdom of Croatia (925–1102)|Croatia]] afterwards. King [[Ladislaus I of Hungary]], on instigation of his sister, Queen [[Helena of Hungary, Queen of Croatia|Helena]], intervenes in the conflict and occupies Croatia. He proclaims himself king, but is contested by the Croatian nobleman [[Petar Snačić]].
* [[February]] &ndash; [[Norman conquest of southern Italy|Norman conquest of Sicily]]: The [[Normans]] conquer [[Noto]] and complete the 30-year-long conquest of [[Sicily]] from the Moorish rulers. Duke [[Roger Borsa]] (a son of [[Robert Guiscard]]) surrenders his share in the castles of [[Calabria]], and receives his inheritance of [[Palermo]]. He grants charters to various towns and encourages [[urban planning]] in [[County of Apulia and Calabria|Apulia and Calabria]]. 
* Summer &ndash; The [[Norman invasion of Malta]]: A Norman fleet led by Count [[Roger I of Sicily]] ("Bosso") arrives in [[Malta]]. Roger disembarks his army, and besieges the island's capital Medina (modern-day [[Mdina]]). The inhabitants negotiate peace terms (by promising to pay an annual [[tribute]]) and swear an oath of loyalty to Roger. On the way back, the Normans sack the island [[Gozo]].
* [[July]] &ndash; The [[Abbadid dynasty]] ruling in [[Al-Andalus]] (modern [[Spain]]) falls when [[Almoravid dynasty|Almoravid]] forces storm [[Seville]]. Confronted with this threat, Emir [[Taifa of Badajoz#Emirs of Badajoz|Muhammad ibn Abu Bakr Muhammad al-Aftas]] of [[Badajoz]] obtains the support of King [[Alfonso VI of León and Castile|Alfonso VI]] ("the Brave") of [[Kingdom of Castile|Castile]], in exchange for the Moorish positions on the river [[Tagus]] ([[Sintra]], [[Santarém, Portugal|Santarém]] and [[Lisbon]]).<ref name=picard2000>{{cite book|last=Picard|first=Christophe|title=Le Portugal musulman (VIIIe-XIIIe siècle. L'Occident d'al-Andalus sous domination islamique|year=2000|publisher=Maisonneuve & Larose|location=Paris|isbn=2-7068-1398-9|page=109}}</ref>

==== Britain and France====
* [[February 2]] &ndash; King [[William II of England]] invades western [[Duchy of Normandy|Normandy]] with a large army. His brothers, [[Henry I of England|Henry]] and [[Robert Curthose]], mobilize mercenary forces to resist him during a siege at [[Mont-Saint-Michel]]. Under terms of the [[Treaty of Caen]], estates on the [[Cotentin Peninsula]] of Normandy are surrendered to William, matters being concluded in August.<ref name=CBH>{{cite book|last=Palmer|first=Alan|last2=Palmer|first2=Veronica|year=1992|title=The Chronology of British History|publisher=Century Ltd|location=London|isbn=0-7126-5616-2}}</ref>
* July &ndash; King [[Malcolm III of Scotland]] invades [[Kingdom of England|England]], reaching as far south as [[Durham, England|Durham]]. The Normans led by William II and Robert march north to oppose the Scots, but a conflict is averted. Malcolm is forced to accept the terms of the [[Treaty of Abernethy]] ([[1072]]) and pays [[Homage (feudal)|homage]] to William.<ref name=CBH/>
* [[Cardiff Castle]] in Wales is constructed by [[Robert Fitzhamon]], Norman lord of [[Feudal barony of Gloucester|Gloucester]] (approximate date).