The religion of the Slavs betrayed its Eastern origin. The supreme deity was called Bog, his wife Siwa; but there were good spirits (_belbog_) to be worshipped and evil ones (_chernebog_) to be propitiated, and every village had its patron divinity.[524] It is possible to carry too far the theory on which Mr. Buckle insisted so strongly--that the destinies of a race are moulded by their physical environment; but its general truth is demonstrated by the history of Russia. The European dominions of the Tsar are an unbroken plain. They contain no mountain fastnesses serving as a refuge for inferior races, and were thus fit arenas for a struggle for existence in which the most vigorous stem of the human family was sure to survive and to expand. And then, Russia lay on the highway of commerce between the East and West. The silks, spices, and sugar of China traversed her plains on their passage to mediæval cities, and the growth of local trade was fostered by the 35,000 miles of navigable river which the empire possesses. To this cause is due the accretion of great urban centres, which played as great a part in Muscovite history as they did in that of Western Europe. These cities were fortified to serve as rendezvous for the surrounding population in time of stress. Their government was strictly democratic; affairs being directed by a general assembly of the citizens, which elected a mayor, a commander of their trained bands, and, later, a bishop. Traders and merchants, who were the backbone of the urban population, were divided into self-governing guilds; and the city, not the individual, sent out its fleets and caravans and colonised distant regions. Each town became a nucleus of a territory whose peasant-inhabitants rendered the City Fathers the allegiance formerly paid to the tribe. With the decay of the tribal conception came radical modifications in the tenure of land. Individualism slowly triumphed over socialism; a class of agriculturists sprang up, who long remained free yeomen. But prisoners of war were reduced to slavery, and freemen who continued in service for more than a year encountered a similar fate. Hence the origin of a great body of serfs, tied down to the soil and acknowledging the mastership of their wealthier brethren. Such was the Russian township in its earlier stages of growth. It was the nidus of a self-governing republic, impelled to expand and conquer by the growth of population which follows increased material prosperity, but powerless to defend itself against foreign aggression. The consciousness of this defect led the citizens to invite soldiers of fortune to lead their militia and give organised means of repelling attack. These adventurers were styled princes (_kniaz_). They were called on to engage to rule according to custom and law. They were bound to keep a body of armed retainers, who were paid by a stipulated tribute.