What was it?
Several contemporary sources tell of a brutal campaign ordered by William the Conqueror against the county of Yorkshire in 1069, when he took vengeance for a rebellion in which his newly established castle at York was destroyed and his men there (including William Malet, Sheriff of York) were killed or carried off by the Danes (Vikings) who had sailed into the Humber to aid the Northumbrians and the men of Yorkshire in their uprising.
William led a huge army north, devastating the land as he went, and recaptured York, which his defeated garrison had already burned to the ground. After he had celebrated Christmas there, William coldly set about a planned devastation of the whole county, splitting his army into smaller bands charged with the task of destroying everything that could support life. This involved the slaughter of people and livestock and the systematic burning of crops and of villages. In the words of the Anglo-Saxon Chronicle, William's harrying of Yorkshire "did for it completely". Another writer, Orderic Vitalis, writing a century later, described the devastation with the words: "He created a wilderness and called it a peace".
Some historians have consequently and quite naturally pointed to the amount of wasteland in the Domesday Book account of Yorkshire (1086) and ascribed this entirely to this campaign of the Conqueror. Further, some have even on occasion referred to the apparent survival of some pockets of settlement as due to 'closeness to the Crown'. However, modern writers question these ideas on several grounds.
Why doubt this reasoning?
1. The history of Yorkshire just before this time is full of war and strife. While still an Earl, the future King Harold had to be sent to the north to end a Northumbrian rising. In 1066, even before the Battle of Hastings, Harold had to march north again (this time as King) to fight off a Viking invasion in which the armies of the North had been shattered at Fulford, after which the Vikings had stormed and captured York. Harold had driven them out after his resounding but largely unknown victory at Stamford Bridge.
2. In the lead-up to the harrying, a Northumbrian army had marched through Yorkshire to York, where the Norman Garrison had set fire to the city and retreated to the castle. The locals made common cause with the Northumbrians, but we cannot assume that this ensured that the rebel armies did no damage to property or person as they passed through the villages and hamlets of the county.
3. Yorkshire is the largest county in England and was even larger in 1086 than it is today. Given the terrain and the lack of roads, it is to be doubted just how completely the area could have been devastated by William's men in a few weeks. It seems more than likely that many pockets of population remained untouched by the devastation and would have been able to colonise deserted villages as soon as the Norman army departed - in the autumn of 1089 when William led his men over the Pennines to meet another uprising around Chester.
4. A year after the 'Harrying', a Scottish army invaded Cumbria and then crossed into Cleveland, carrying off men and animals as booty. Why would he raid an area where there was nothing left to pillage?
5. During the rest of William's reign, Northumbrian forces marching south to attack the Normans, and Norman armies marching North against the Scots and the Northumbrians became a regular feature of the history of the north. Danish fleets were frequently off the coast, and all of these armed forces would have without doubt have demanded or seized the supplies that they wanted from the hapless population. Indeed, in the northern uprising of 1084, again involving the Vikings, together with the few surviving members of the old Saxon nobility and Scottish armies under King Malcolm, William is known to have ordered the 'wasting' of coastal areas so as to prevent his enemies finding supplies. It was this uprising, the most threatening of his reign, which caused him to bring into England more armed men than the country had ever seen before, and indirectly led to the Domesday Survey. The Saxon nobility may have been the leaders, but the ordinary people would doubtless have suffered again. Even in modern times, with the Geneva Conventions, the International Court at the Hague and the court of international opinion to protect them, we have countless instances of the massacre and genetic cleansing of civilians. It stretches the bounds of credibility to suggest that the same and worse did not occur at a time when a new foreign Norman elite was struggling to contain a resentful and rebellious native Anglo-Saxon/Anglo-Scandinavian population.
6. Ascribing survivals to 'closeness to the crown' does not bear examination. It would mean believing that all the members of the 1069 Norman raiding parties would have to know whose lands they were on at every stage of the process, so that the devastation would be selective: this at a time when Domesday Book was twenty years into the future and the Frenchmen under William's command could hardly be expected to speak the English tongue. Again, when the King's own Yorkshire lands are examined, the picture is as bad as that of the holdings of any other landowner. Huge, previously rich Royal Manors like Northallerton, Pickering, Easingwold, Driffield and Pocklington were partially or totally wasted. The total value of these manors alone had fallen from £296 to £10 and 4 pence. Either William deliberately despoiled his own estates, did not realise he was doing it, or his estates were despoiled by his enemies! In whichever case, closeness to the Crown did not save them!
Summary
Rather than the harrying representing the one calamitous event that caused all the devastation evidenced in Domesday, it is probably better seen as one particularly savage incident among countless savage events occurring all through the Conqueror's reign which were collectively responsible for the amount of waste land in the county. And in all probability, Vikings, Scots and Northumbrians were all culprits, as well as the Conqueror.
Nor did William I's death end the misery. Northern barons were deeply involved in a rebellion against the Conqueror's son, William Rufus, within a few months of his accession in 1187. We can be sure that once more, the ordinary folk bore a disproportionate amount of the pain.
What cannot be denied is that Yorkshire was in a worse state when the Conqueror died than it had been in the reign of Edward the Confessor, and that its recovery was hardly in prospect even in 1100AD.