The 1066 invasion in which William, Duke of Normandy, seized the English throne, defeating and killing King Harold at the Battle of Hastings and being crowned on Christmas Day as William the Conqueror. It was the last successful foreign conquest of England, and it remade the country's ruling class, language, law, and landscape so completely that the result is still audible in modern English. The conquest was brutal, marked by the devastating Harrying of the North, and it left behind both a fused English language and the lasting myth of a free Anglo-Saxon age crushed by a Norman yoke.
England has not been successfully invaded since 1066, and the man who did it last changed the country so deeply that you can still hear it when you speak. In that year the English king died without a clear heir, three men claimed the throne, and a duke from northern France crossed the Channel to take it. At a hill near Hastings, William of Normandy defeated and killed King Harold, by legend with an arrow through the eye, and on Christmas Day he was crowned William the Conqueror. Then he did something rarer than winning a battle. He swept away nearly the entire English ruling class and handed their lands to his own followers. A French-speaking elite now ruled an English-speaking people, and over the centuries the two tongues fused, which is why English keeps the farmer's word cow beside the lord's word beef. The takeover was bloody, the dispossession near-total, and England has stayed an island no army has conquered since.