The battle was waged over the throne of England.
When the English king Edward the Confessor died, there were several contenders for the throne.
Harold Godwinson was in England at the time and was proclaimed king by the Witan, a council of nobles and priests.
The Norman William the Bastard also laid claim and prepared an invasion, but was held up by bad weather.
Before he could move, the third contender, king Harald Sigurdsson of Norway, landed in Northumbria.
Harold force-marched north and beat Harald at the Battle of Stamford Bridge,
but shortly after the weather cleared and allowed the Normans to sail across the Channel and land unopposed.
They built a wooden castle from prefabricated parts they had brought with them.
Harold marched back south to meet them.
The size of the opposing forces is unclear.
Modern estimates range from 7,000 to 12,000 for the Normans, possibly 1/4 cavalry, 1/5 archers and the rest foot soldiers,
and a roughly equal number for the Saxons, a minority of housecarls supplemented with fyrd levies, all infantry.
Harold's men were tired from the march to and from Northumbria and the battle there,
but he rested them for a week in London before engaging William.
It seems that William forced Harold into battle by pillaging the countryside.
When scouts reported that Harold moved to Hastings, the Normans marched out of their makeshift fort too and engaged them.
Both sides hurried to gain the best position; Harold reached Caldbec hill first, where his flanks were protected by woodland and marsh.
Harold deployed his army in a strong shield wall on the hill.
William divided his forces in three: Bretons on the left, French on the right and himself with his Normans in the center.
Archers opened the battle, but shooting uphill, achieved little against the solid shieldwall.
Infantry and then cavalry followed up, also without success.
After a few hours the Bretons started to retreat and the Saxons, foolishly, pursued.
A rumor spread that William had been killed, but he quickly showed himself without helmet to quell that idea.
The Normans mounted a counterattack and drove the Saxons back, inflicting the first significant losses.
In the afternoon, after a little rest, the Normans made the morning maneuver into a deliberate tactic at least twice,
feigning flight and then wheeling around for a counterstrike.
This thinned the ranks of the Saxons, yet did not break them.
At some point Harold fell, probably by a sword blow.
After that the Saxon line started to disintegrate and they were routed.
Only the housecarls stayed put and fought until the bitter end, lasting until nightfall.
Again casualty numbers are vague.
Probably the Normans lost a few thousand men and the Saxons more.
Hastings allowed William to gain the crown and become William the Conqueror,
though he had to fight for four more years until all enemy resistance had been eliminated.
The Norman attack was the last that conquered England from the mainland.
Never after was an invasion of Britain successful.
War Matrix - Battle of Hastings
Viking Age 800 CE - 1066 CE, Battles and sieges