Russian Empire
Though the Empire was only officially proclaimed by Tsar Peter I following the Treaty of Nystad (1721), some historians would argue that it was truly born either when Ivan III of Russia conquered Veliky Novgorod in 1478, or when Ivan the Terrible conquered the Khanate of Kazan in 1552. According to another point of view, the term "Tsardom", which was used after the coronation of Ivan IV in 1547, was already a contemporary Russian word for empire.
History of Russia
In this way, internal consolidation accompanied outward expansion of the state. By the 16th century, the rulers of Moscow considered the entire Russian territory their collective property. Various semi-independent princes still claimed specific territories, but Ivan III forced the lesser princes to acknowledge the grand prince of Moscow and his descendants as unquestioned rulers with control over military, judicial, and foreign affairs. Gradually, the Russian ruler emerged as a powerful, autocratic ruler, a tsar. The first Russian ruler to officially crown himself "Tsar" was Ivan IV.