The most famous, the Battle of Crogen, took place in 1165 near what is now called Castle Mill, Chirk, when Welsh forces defeated Henry II's men.
A plaque was installed near another battle site at Pont Rhyd y Gad bridge at Tre Ceiriog on Saturday.
It commemorates the wider Berwyn Mountain campaign.
Re-enactment group Cwmwd Ial staged a living camp to mark the anniversary.
It was in late July 1165 that Henry gathered a vast army at Oswestry, Shropshire, while the opposing forces of the Welsh princes waited near Corwen, Denbighshire.
When his terms were turned down by the Welsh allies, Henry's army made their way up through the Ceiriog Valley.
Despite being outnumbered, the Welsh forces were able to raid and ambush Henry's army, inflicting heavy losses.
The Battle of Crogen, along with atrocious weather, meant that Henry's army was eventually forced to leave Wales altogether, retreating to Chester.
A commemorative plaque is unveiled in the Ceiriog Valley to mark the 850th anniversary of a series of battles between Welsh and English forces.