With the Norwegian army destroyed, Harold turned back south to face the fleet of William, who had invaded as quickly as he had the chance. The Norman had some 7000 men in his army, powerful knights and mercenaries. Harold had a similar number, primarily ax men, and the advantage of defense. Harold fortified a ridge at Hastings and readied their defensive shield wall, which stopped the onslaught of Norman arrows, even those from the cutting edge technology known as crossbows.
The Norman infantry charged uphill, and the English fought back, throwing rocks and javelins. Unwounded by the barrage of arrows, the English held firm and drove the Normans back. Harold's men, including his two surviving brothers, began pursuit. In the confusion, William fell, but his triumphant stand and tossing his helmet rallied his soldiers to counter-attack. Harold's brothers were slain, and the Normans charged with additional arrow barraged. William aimed directly for Harold, who realized that he alone was the English heir to the throne with his brothers gone. Norway had been deprived of its king in battle, and now England might, too.
Calling for a last desperate defense, Harold began the retreat. The rearguard took heavy casualties from the Norman knights, who took up pursuit until they were caught on steep ground in the night and were slaughtered in ambush at the Malfosse or “Bad Ditch.” The Normans had won the battle, but Harold and the English were still a force. Morale sank, but Harold reminded his men that they had lost to Harald at Fulford and then smashed him at Stamford Bridge. He who had bravely rode up alone to face Harald would lead them to victory no matter how many battles it took.
William pressed, sending Harold from Sussex back to London, but the campaign season ended as winter came on. The Normans took losses from dysentery, with even William himself falling ill, but fresh troops arrived from across the English Channel. Harold called up reinforcements himself, attempting to unite the English in defense, but many nobles held that the dispute was a family matter between Harold and William. Some nobles politicked with Normandy over the winter and became supporters of William.
In spring, war resumed in what many called William's War or the Anglo-Norman War. Harold had the home-field advantage while William had international support from the Church's blessing. The armies checked one another, devastating southern England and at one point even driving Harold as far as Chester. Finally, in 1072, Harold drove William from England back across the Channel.
The war had been won, but it had crippled England. Normandy survived with enormous debts, but whole towns of England had been put to the torch. While they would rebuild and grow in strength, they would be outpaced by their Celtic neighbors to the north with the rise of Robert the Bruce in 1306. His brother Edward became king of Ireland in 1316, affirming his position in 1318 by handily defeating an army of Irish lords backed by the English at the Battle of Faughart. In later wars with the English, the Bruce would add Wales to their holdings and eventually merge the clans under one crown in the Gaelic Union.
The English were pushed farther and farther southeast until they were something of a republican city-state around London ruled by their Parliament.
In reality, Alfred was killed at Hastings. William would march on London and be crowned king on Christmas Day. Normans would achieve noble control over the Saxons, beginning the complicated mix of language and culture that eventually gave us the fluid modern English.