Owain of Gwynedd, prince of north Wales, and Rhys ap Gruffydd, leader of south Wales, reconquer lands earlier taken from them by the Anglo-Normans.
King Henry II (who had ascended to the throne in 1154) decides to invade Gwynedd to halt the recent expansion of Owain into the lands of Powys, and to expand his empire into northern Wales.
With the support of the Prince of Powys Madog ap Maredudd and Owain's brother Cadwaladr ap Gruffydd (who Owain had recently stripped of his lands in Ceredigion), Henry leads a large army (claimed to be as many as thirty thousand men) into northern Wales and sends a fleet (led by Henry FitzRoy) to capture Anglesey to cut off Owain's supplies.
Owain responds by raising a Welsh army of around three thousand men.
Owain's army makes camp at Basingwerk to block the route to Rhuddlan.
Henry splits from his main army with a smaller force that will march through the nearby Ewloe woods (near Flintshire) to outflank Owain's army.
Sensing this, Owain is said to have sent a large army led by his sons Dafydd ab Owain Gwynedd and Cynan ab Owain Gwynedd into the woods to guard Owain's main force from Henry's outflanking army.
Owain splits his army and decides to personally lead an extra two hundred men into the Ewloe woods to reinforce his sons' armies.
When Henry's outflanking force advances into the wood, they are ambushed by Owain's forces and cut down.
The remainder of Henry's force retreat, with Henry narrowly avoiding being killed himself (having been rescued by Roger, Earl of Hertford).
Henry manages to escape back to his main army alive.
Not wishing to engage the Angevin army directly, Owain repositions himself first at St. Asaph, then further west, clearing the road for Henry II to enter into Rhuddlan "ingloriously".
Once in Rhuddlan, Henry II receives word that his naval expedition hadfailed.
Instead of meeting Henry II at Deganwy or Rhuddlan as the king had commanded, the English fleet had gone to plunder Môn and the Norman troops on board had been defeated by the local Welsh soldiers (Henry FitzRoy himself had also been killed).
Despite Owain's success in the Ewloe woods and his men on Anglesey's success, Henry has still succeeded in securing Rhuddlan, so Owain feels obliged to make peace with him.
Owain surrenders the lands of Rhuddlan and Tegeingl to Chester.
He also returns to Cadwaladr his lands in Ceredigion, which re-cements the alliance between the two brothers.
Owain also agrees to render homage and fealty to Henry.