the Eastern branch of the Slavs, speaking a closely related group of dialects. The political unification of this region into Kievan Rus' in about 880, from which modern Russia, Ukraine, and Belarus trace their origins, established Old East Slavic as a literary and commercial language. It was soon followed by the adoption of Christianity in 988 and the introduction of the South Slavic Old Church Slavonic as the liturgical and official language. Borrowings and calques from Byzantine Greek began to enter the Old East Slavic and spoken dialects at this time, which in their turn modified the Old Church Slavonic as well. Dialectal differentiation accelerated after the breakup of Kievan Rus' in approximately 1100. On the territories of modern Belarus and Ukraine emerged Ruthenian and in modern Russia medieval Russian. They became distinct since the 13th century, i.e. following the division of the land between the Grand Duchy of Lithuania and the Poland in the west and independent Novgorod and Pskov feudal republics plus numerous small duchies (which came to be vassals of the Tatars) in the east. The official language in Moscow and Novgorod, and later, in the growing Muscovy, was Church Slavonic, which evolved from Old Church Slavonic and remained the literary language for centuries, until the Petrine age, when its usage became limited to biblical and liturgical texts. Russian developed under a strong influence of Church Slavonic until the close of the 17th century; afterward the influence reversed, leading to corruption of liturgical texts. The political reforms of Peter the Great (Пётр Вели́кий, Pyótr Velíky) were accompanied by a reform of the alphabet, and achieved their goal of secularization and Westernization. Blocks of specialized vocabulary were adopted from the languages of Western Europe. By 1800, a significant portion of the gentry spoke French daily, and German sometimes. Many Russian novels of the 19th century, e.g. Leo Tolstoy's (Лев Толсто́й) War and Peace'', contain entire paragraphs and even pages in French with no translation given, with an assumption that educated readers would not need one. The modern literary language is usually considered to date from the time of Alexander Pushkin () in the first third of the 19th century. Pushkin revolutionized Russian literature by rejecting archaic grammar and vocabulary (so-called — "high style") in favor of grammar and vocabulary found in the spoken language of the time. Even modern readers of younger age may only experience slight difficulties