Feudalism is the name given to the system of government William I introduced to England after he defeated Harold at the Battle of Hastings. Feudalism became a way of life in Medieval England and remained so for many centuries.
William I is better known as William the Conqueror. He had defeated the English army lead by Harold but he had to gain control of all of England before he could be truly called king of England. He was a foreigner who had forced his way to London. He was not popular with the people of England and he had to use force to maintain his control on England.
William could not rule every part of the country himself - this was physically impossible. Not only was travel difficult and slow in the eleventh century, he was also still Duke of Normandy and he had to return to Normandy to maintain his control of this land in France. Therefore, he had to leave the country for weeks at a time. He needed a way of controlling England so that the people remained loyal.
William spent much of his time in London. He built his own castle - the Tower of London - so that it dominated the city. It was also his home while in London. He did not trust the builders of London - or English stone - so he used Norman craftsmen to do the skilled work while the English acted as labourers and he brought in from Caen (in France) the stone needed for what we now call the White Tower. He also built the first castle at Windsor. The motte is still visible. Castles represented a visible threat to the people of England. Soldiers were kept in them and they could be used against the English should they cause trouble.
However, he needed a way of actually governing the country. This was the Feudal System.
William divided up England into very large plots of land - similar to our counties today. These were 'given' to those noblemen who had fought bravely for him in battle. William argued that those noblemen who were willing to die in battle for him, would also be loyal to him. The land was not simply given to these nobles. They had to swear an oath of loyalty to William, they had to collect taxes in their area for him and they had to provide the king with soldiers if they were told to do so. In the eleventh century, a sworn oath on the Bible was a very important thing and one which few men would dare to break as it would condemn them to Hell. The men who got these parcels of land would have been barons, earls and dukes Within their own area, they were the most important person there. In the terms of the Feudal System, these men, the barons etc., were known as tenants-in-chief.
Even these pieces of land were large and difficult to govern.
The barons etc. had to further divide up their land and these were 'given' to trusted Norman knights who had also fought well in battle. Each knight was given a segment of land to govern. He had to swear an oath to the baron, duke or earl, collect taxes when told to do so and provide soldiers from his land when they were needed.
It was argued, that because they had sworn an oath to their baron, they had really sworn an oath to the king. These lords worked to maintain law and order. The people in their land - or manors - were treated harshly and there was always the constant threat of Norman soldiers being used against the English people where ever they lived. The lords had to do their job well as unsuccessful ones could be removed from their position. Their job was simple - keep the English people in their place......under the control of the Normans. Under the Feudal System, these men, the knights, were called sub-tenants.
Note that both groups were officially tenants - a word we associate with land that does not belong to you. Both all but rented out their land in that they had to provide money or services to the real owner of all land - William the Conqueror.
At the bottom of the ladder were the conquered English who had to do what they were told or pay the price for their disobedience.
There is no doubt that William's rule was harsh. But he was a man who had conquered the country. He was not in England through the popular choice of the people and he had to ensure that he had full control over them at all times. He ensured that there were obvious signs of his power - the country saw the building of many Norman castles. He also knew what was owed to him because he ordered a survey of the whole country - the Domesday Book.