Madog ap Maredudd had died in 1160, enabling Owain Gwynedd to regain territory in the east.
He had formed an alliance in 1163 with Rhys ap Gruffydd of Deheubarth to challenge English rule.
Henry II, who has ordered the reconstruction of a number of fortresses in the Welsh marches, gain invades Gwynedd in 1165, but instead of taking the usual route along the northern coastal plain, the king's army invades from Oswestry and takes a route over the Berwyn hills.
The invasion is met by an alliance of all the Welsh princes, with Owain as the undisputed leader.
However, apart from a small melee at the Battle of Crogen there is little fighting, for the Welsh weather comes to Owain's assistance as torrential rain forces Henry to retreat in disorder.
The infuriated Henry mutilates a number of Welsh hostages, including two of Owain's sons.
Henry now has additional fortresses built.
