After the break-up of the Roman Empire, when there were no strong central governments in Europe, when practically the only law was the will of the strongest, it was inevitable that a vast number of petty chieftains should gather about them as many followers as possible, both in order to protect themselves and to plunder others. The ablest of these, by waging a continual warfare, either killed off many of their rivals and took possession of their lands, or reduced them to submission and made them tenants of their own. These tenants held their land only on condition of furnishing a certain number of men for their lord's wars and paying certain taxes, later called "aids," for his support. When this state of society became finally organized as the feudal system, the king or emperor was the overlord, the counts swore allegiance to him, the petty nobles and knights were tenants in their turn. By the twelfth century, the counts and bishops were little kings in their own domains. They had gradually acquired all the rights of the crown. They coined money, established markets, acquired the rights of fishing, hunting, brewing and milling, and collected the tolls. They were vassals of the king in little more than name. Below this landed aristocracy were the two classes of villains and serfs, who led a miserable existence, possessing scarcely one of what we consider the inalienable rights of man. Both villains and serfs were slaves, bound to the soil, but the servitude of the latter was hopeless and irremediable. Serfs must always be serfs. But the villains had the privilege of earning their freedom. When Peter the Hermit, a Walloon of the province of Liège, made his impassioned appeals to Christendom to rescue the Holy Sepulcher from the Saracen, it was Godfrey of Bouillon, another Walloon, who laid aside his titles and sold his possessions that he might equip an army for the conquest of the Holy Land. Godfrey was made "Advocate" of Jerusalem, and was the first Western ruler of the sacred city. His brother Baldwin became King of Edessa, in Mesopotamia, and his descendants were kings of Jerusalem. Next to Godfrey, both as knight and leader, stood Count Robert of Flanders. It is told of Philip of Alsace, Count of Flanders, that he challenged and defeated a mighty Saracen in single combat. The device on his shield, which Philip bore away as a trophy, was a black lion on a field of gold. This became the emblem of Flanders. But Philip of Alsace was noted not alone for his prowess in battle; he was an enlightened ruler for his age. He resigned the privileges of "mainmorte" and "half-have." By "mainmorte," if a man died without leaving direct heirs, his property went to the count. By "half-have," half of all the property left by any of his vassals went to the count.