A traditional rivalry between
Brittany and
Normandy continued at the close of the 11th century. The Breton-Norman war of 1064–1065 was the result of
William the Bastard, Duke of Normandy (later to become known as William the Conqueror) support of rebels in Brittany against Alan's maternal uncle,
Conan II. Conan II died in late 1066 during a campaign in Anjou, and was succeeded by Alan's parents,
Hawise and
Hoël II. When Hawise died in 1072, Alan became duke, but as he was a minor, Hoël ruled as regent until Alan reached his majority in 1084. To prevent further hostilities during his invasion of England, William I married his daughter
Constance to the new duke Alan in 1087. The marriage ceremonies may have taken place in
Bayeux in Normandy.
William of Malmesbury wrote that Constance was unpopular at the Breton court because of her "severe and conservative" manner. However,
Orderic Vitalis wrote that as duchess Constance did all she could to further the welfare of the Bretons, who grieved deeply at her death in 1090. In 1092, Alan IV donated property to the
abbey of Redon by charter, and by 1093 married
Ermengarde of Anjou, as a political alliance with
Fulk IV of Anjou to counter Anglo-Norman influence. , the final resting place of Alan IV Duke Alan IV's cousin Geoffrey I Boterel (eldest brother of
Alan Rufus) died on 24 August 1093 in battle at Dol while in rebellion against the Duke. Between 1101 and 1104, Alan's younger brother, Count
Matthew II of Nantes, died without issue and his county passed to Alan. Alan IV abdicated as duke in 1112. The former duke retired to the monastery of Redon, where he died in 1119. ==Crusader==