For over two hundred years most of Russia was under the control of the Mongol
whose capital was at Kazan on the Volga river.
The Mongols (or Tartars as the Russians called them) had used the Grand Duke of Moscow to collect taxes for them. This contributed to the rise of the grand dukes of Moscow, and it was eventually a Moscow-led alliance that broke the power of the Tartars.
Tartar rule over much of Russia came to an end in 1480, after the advent of artillery and guns had made the Tartar cavalry archers of the steppes ineffective. Protected by an impregnable citadel (the Kremlin) which was defended by artillery.
Ivan III renounced his allegiance to the Mongols and assumed the title of tsar, which meant that Moscow became the capital of an independent Russian state.