Anglo-Saxon & Norman England c1060–88

One reason William won was that¹ Harold's army was weakened and tired by having to fight on two fronts. In September 1066 Harald Hardrada and Tostig invaded the north, defeating the northern earls Edwin and Morcar at Fulford on 20 September². Harold marched north and won a great victory at Stamford Bridge on 25 September, but lost many of his best housecarls. Only three days later, on 28 September, William landed at Pevensey on the south coast. Harold marched his army around 200 miles back south and chose to fight on 14 October rather than wait in London for more troops to gather. This meant that many of Harold's soldiers were exhausted³, and his army included poorly armed men from the fyrd rather than a full force of trained warriors, which made it harder to hold out for a full day's fighting.

A second reason was William's use of cavalry and tactics. The English fought on foot in a shield wall along the top of Senlac Ridge, which at first was very strong: Norman archers and charges up the slope failed to break it. However, William's mounted knights could move quickly and turn to attack. When part of William's army fled and a rumour spread that William had been killed, he lifted his helmet to show he was alive, and his cavalry cut down the English soldiers who had broken ranks to chase them. The Normans then used this deliberately with feigned retreats⁴, luring more men out of the shield wall and killing them on the open ground. This mattered because, once the shield wall thinned, the English could no longer keep out the combined attacks of archers, infantry and cavalry.

A third reason was William's careful preparation and good fortune⁵. He had won the support of Pope Alexander II, who sent a papal banner, which made the invasion look like a holy cause and helped him recruit knights from across France. He also built a large fleet and gathered supplies in Normandy. Unfavourable winds kept his ships in port through the summer, but this delay turned out to be lucky: Harold had kept the fyrd guarding the south coast all summer, but had to send it home on 8 September because its supplies had run out and the harvest needed gathering. As a result, William landed without any opposition and had two weeks to build a castle at Hastings and rest his troops before the battle.

These reasons were linked⁶. William's preparation and luck allowed him to land safely, Harold's rush south meant he fought with a tired and incomplete army, and this made the Norman tactics of cavalry charges and feigned retreats much more effective. The death of Harold and his brothers Gyrth and Leofwine during the battle left the English with no leader, and their army collapsed.

I agree with the statement to some extent¹. Castles were the most widespread and immediate method William used to control England, and every other method depended on them. However, castles alone could not prevent major rebellions, as the events of 1069 showed; the Harrying of the North and the transfer of land to Norman lords were also needed to make Norman control secure by 1075.

Castles were very important because they let a small number of Normans control a large, hostile population. Motte and bailey castles could be built quickly – often in a few weeks – using forced local labour, earth and timber. William built them in strategic places, such as towns, river crossings and roads. For example, after the revolt in Exeter in 1068 he built a castle inside the city walls², and during his campaign north in 1068 he built castles at Warwick, Nottingham and York. Each castle held a garrison of knights who could ride out to stop trouble and collect taxes, and the motte gave a view over the surrounding area. Castles were also a powerful symbol: houses were often knocked down to make room for them, reminding the English who was now in charge. This meant that the Normans could control towns³ and the surrounding countryside even though they were vastly outnumbered.

However, castles were not enough on their own, as the rebellion of 1069 showed⁴. Edgar Aethling and northern rebels, supported by a Danish fleet sent by King Sweyn, attacked York and destroyed its castles, killing hundreds of Normans. William's response was the Harrying of the North in the winter of 1069–70. His soldiers destroyed villages, crops, livestock and ploughs across Yorkshire and beyond, causing famine. The chronicler Orderic Vitalis, writing decades later⁵, claimed that 100,000 people died, and the Domesday Book of 1086 recorded large areas of Yorkshire as 'waste'. This was highly effective: the north had been the most rebellious region, and after 1070 it never again rose against William. The Harrying therefore achieved something castles had failed to do, by removing the people and resources that rebellion relied on.

Another key factor was the way William changed who held the land. After the rebellions of 1068–71, English earls and thegns lost their land, which was given to William's Norman followers as tenants-in-chief in return for loyalty and knight service. William created compact Marcher earldoms⁶ on the Welsh border, at Hereford, Shrewsbury and Chester, giving trusted men such as William FitzOsbern the power to defend these areas. In the Church, he replaced Archbishop Stigand with the Norman Lanfranc in 1070. This meant that the people with power and wealth in England increasingly owed everything to William, so there were fewer English leaders around whom a revolt could form. When three earls did rebel in 1075, the revolt failed because other Norman lords and the Church stayed loyal; the English earl Waltheof was executed in 1076. This factor links to castles, because the new Norman lords built and garrisoned castles on their land.

Overall, I partly agree with the statement. If the test is which method was used most widely and gave William control from the start, castles were the most important. But the best test of 'main' reason is what made control last. Here, castles failed in 1069, and it was the Harrying of the North and the replacement of the English landholding elite that ended large-scale resistance. Castles were therefore necessary for Norman control, but not, by themselves, sufficient⁷.