The development of feudal society in the region of Rus' took a different course to that in Western Europe. In particular, under the version of manorialism practised in Rus', knights granted land by a prince were not bound in allegiance to that prince; and instead of serfdom much of the land was worked by a partially free peasant class (smerd). In consequence, there was no strong central monarchy able to resist invasions by the Lithuanians, Tatars and Mongols. A strong central power emerged only later, particularly under Ivan III of Russia, which defeated the invaders, unified the territory of Rus', and laid claim to large areas of land. Origins of Russian/Muscovite manorialism At the end of the first millennium AD, Europe was experiencing the full effects of the order and advances in social structure begun during the early Middle Ages; however, the structure and development(s) characterising medieval European society were not found beyond the Carpathian Mountains, and the region of Rus' remained as a disordered regionalist "state". The early development of feudal society in the absence of a strong central government helped the European states overcome the harshness experienced in the Dark Ages by enabling the creation of strong governments. In Western Europe, a manorial (economic)/feudal (political) system was created, culminating in the full development of feudal society spreading across Europe and to England; a society which divided land, top to bottom, from the monarch to his immediate trustee or vassal, to the peasant or serf, who worked the fiefs in tribute, in return for protection from invaders. This symbiotic system created the first central governments throughout Christendom since the fall of Rome. The history of Eastern Europe, Rus' in particular, was different. Due to the expansion of trade and its geographical proximity, Kiev became the most important trade center of Kievan Rus' and chief among the communes; therefore the leader of Kiev gained political "control" over the surrounding areas. This princedom emerged from a coalition of nuclear families banded together in an effort to increase the available workforce and expand the productivity of the land. This union developed the first major cities in Rus' and was the first notable form of self-government. As these communes became larger, the emphasis was taken off the family holdings and placed on the territory that surrounded them. This shift in ideology became known as the verv'. The change in political structure led to