Feudalism, a term first used in the seventeenth century (the word comes from feudum, a fief or grant of land), became the political and social system characteristic of western Europe during the Middle Ages. This system evolved over many centuries. After the collapse of the Roman Empire in the fourth century, Europe experienced a breakdown of law and order and a decline in living standards. During a brief period at the end of the eighth and beginning of the ninth century the great warlord and emperor Charlemagne and his heirs established a central government, but Charlemagne’s three grandsons soon broke up the empire into separate kingdoms. As the Carolingian empire gave way to internal strife and outside dangers, rival families fought for wealth and power. Meanwhile, Vikings, Slavs, Magyars (Hungarians), and Muslims threatened western Europe. Local strongmen led bands of warriors and formed private armies. They lived in timber blockhouses and towers set behind earthworks and stockades. For a price they took farmers under their protection. What was at first a simple agreement between a military chief and the civilians who needed protection slowly evolved into a system of formal oaths and grants of land. The Celtic/Germanic warrior tradition of a lord and his people bound by oaths of loyalty and mutual support joined with the ancient Roman idea of patrons who retained their land but made grants to clients or tenant farmers. By the tenth and eleventh centuries this system of lords and vassals, known today as feudalism, replaced kingdoms and empires, and effective government lay in the hands of private individuals. During the Middle Ages, land (not money) was the basis of wealth, power, and authority, and a very small group of men—and a few women—controlled the land. As the political and economic system evolved, especially in France and England, the king, who in theory held the land in trust for God, gave his powerful friends parcels of land to exploit in exchange for military support and assistance in administering justice. Vassals would owe service in the feudal lord’s army and in his court, in exchange for food and lodging at the lord’s castle. But the expense of maintaining an army and running a castle was enormous. As a result, major landholders complicated the system by subdividing and parceling out their lands to retainers under similar terms. As a money economy began to develop, it became convenient for the vassal to pay the lord instead of performing service. This was known as “shield money” or “scutage.” Eventually landholding became hereditary, with titles, duties, and resources passed on from father to children, in most cases to the oldest son. Never as neat or well organized as many descriptions suggest, in essence feudalism involved the exchange of grants of land for military and political service, sealed by personal oaths between the lord and the vassal. The castle has been called the perfect architectural expression of the European feudal age.