During the Middle Ages, peasants could no longer count on the Roman army to protect them. German, Viking and Magyar tribes overran homes and farms throughout Europe. The peasants turned to the landowners, often called lords, to protect them. Some peasants remained free, but many became serfs. A serf was bound to the land. He could not leave without buying his freedom, an unlikely occurrence in the Middle Ages. Life for a serf was not much better than the life of a slave. The only difference was that a serf could not be sold to another manor.