Whenever any ruler, whether he was a king or only a prince, conquered another ruler, he gave to his generals, who had fought with him and helped him to win, pieces of the conquered land as a reward instead of paying them in money. The generals in turn gave pieces of their land to the chief men who had been under them and helped them in battle. These men who were given land were called lords or nobles, and each lord was called a vassal of him who gave the land. Each vassal had to promise to fight with his lord whenever he was needed. He could not make this promise lightly in an offhand way, however. He had to do it formally so that it would seem more binding. So the vassal had to kneel in front of his lord, place his folded hands between the folded hands of his lord, and make the solemn promise to fight when called upon. This was called “doing homage.” Then once a year, at least, thereafter, he had to make the same promise over again. This method of giving away land was known as the Feudal System. [Illustration: Castle, drawbridge, moat and knights.] Each of these lords or nobles then built himself a castle on the land that was given him, and there he lived like a little king with all his work-people about him. The castle was not only his home, but it had to be a fort as well to protect him from other lords who might try to take his castle away from him. So he usually placed it on the top of a hill or a cliff, so that the enemy could not reach it easily, if at all. It had great stone walls often ten feet or more thick. Surrounding the walls there was usually a ditch called a moat filled with water to make it more difficult for an enemy to get into the castle. In times of peace when there was no fighting the men farmed the land outside of the castle; but when there was war between lords, all the people went inside the castle walls, carrying all the food and cattle and everything else they had, so that they could live there for months or even years while the fighting was going on. A castle, therefore, had to be very large to hold so many people and animals for so long a time, and often it was really like a walled town. Inside the walls of the castle were many smaller buildings to house the people and animals and for cooking and storing the food. There might even be a church or chapel. The chief building was, of course, the house of the lord himself and this was called the _keep_.