Between 1450-1700, Russia grew from a loose federation of states centered around Kiev into a vast empire dominated by the Tsars. The Mongol invasion in the 13th century brought Russia under Mongol rule until the 1400s. The first Tsars expanded the Russian state into Siberia and Central Asia while centralizing power. Conflict between nobles and Tsars led to civil wars. The Romanov Dynasty established rule from 1613-1914 after a period of turmoil. Peter the Great forcibly Westernized Russia in the early 1700s through reforms like a modernized army and navy as well as the founding of St. Petersburg, but serfdom and oppression of lower classes continued.