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In 1558 Ivan gave the Stroganov merchant family the patent for colonizing an area east of the Urals. They built many forts and later hired Cossacks to protect their lands. The Tartars had by then established another Khanate in Siberia.<ref>Bobrick, p. 116</ref> The Cossack leader in 1580 began the conquest of Siberia, and he forced many local tribes to pay tribute to Moscow. Later Ivan sent a large force of Streltsi or members of his army to assist in the conquest. By 1590 Ivan was also calling himself Tsar of Siberia. Ivan died of a stroke while playing chess and his middle son Feodor succeeded him. Russia at the time of his death was at the strongest it had in several centuries.

====Ivan and the Orthodox Church====