Final answer:
The Mongols were the force that dominated the Russian region for over 150 years after their invasion in 1240 C.E., controlling various Russian city-states until the Russian principalities started to unify and overthrow their rule.
Step-by-step explanation:
The Dominant Forces in the Russian Region
The dominant force that controlled the Russian region for more than 150 years were the Mongols. After Genghis Khan's Mongol Empire invaded in 1240 C.E., they conquered and ruled over various Russian city-states. This invasion had profound and enduring effects on the region's development, including the shifting of influence from Kiev to Moscow. The Mongol control, often referred to as the "Tatar Yoke," lasted until the latter part of the 15th century when the Russian principalities, under the leadership of the princes of Muscovy, began to consolidate power and throw off Mongol dominance. Despite the attempts of various Russian city-states to defend themselves, the feuding among them made resistance to Mongol rule ineffective and prolonged their control over the region.
In contrast, although the Vikings created fortified trading towns called gorods and had a significant influence on the early development of the Russian state, their dominance did not extend beyond the formation of early Russian principalities. They were essential in establishing trade routes and in the expansion of trade, particularly with the Byzantine Empire, which had a lasting impact on the culture and economy of the region. However, their direct control did not last nearly as long as that of the Mongols.