sentences:  The period includes the upheavals of the transition from the Rurik to the Romanov dynasties, many wars with the Polish–Lithuanian Commonwealth, Sweden and the Ottoman Empire as well as the Russian conquest of Siberia, leading up to the ground-changing reign of Peter the Great, who took power in 1689 and transformed the Tsardom into a major European power.During the Great Northern War, he implemented substantial reforms and proclaimed the Russian Empire (, "Rossiyskaya imperiya") after victory over Sweden in 1721.While the oldest endonyms of the Grand Duchy of Moscow used in its documents were "Rus"' () and the "Russian land" (), a new form of its name, "Rusia" or "Russia", appeared and became common in the 15th century.