Battle of Hastings
The Battle of Hastings (1066) was a decisive battle in which the Normans led by William the Conquerer defeated the Anglo-Saxons, under Harold Godwinson. It was the last time Great Britain was conquered by an outside power.
Harold made some strategic mistakes heading into the battle. He had just repelled an invasion by Harald Hardrada in the north, and rushed his weary army to the south in response to William's landing and provocation. Had he rested his army first, he could have taken advantage of the friendly country while William would have encountered logistical problems.
The day of the battle the Anglo-Saxons for the most part fought well, but were lured off the ridge they were defending by a Norman retreat (real or feigned) where a large number were easily cut down by the Norman knights. Harold was eventually hit in the eye by an arrow and what remained of the Saxon defense dissolved.
The Normans conducted several mopping up campaigns in the aftermath, including a genocidal rampage through northern England called the "Harrowing of the North".
The history of the battle was recorded in the Bayeux Tapestry.