Old East Slavic in the context of The Tale of Igor's Campaign

The Lithuanians or Old East Lithuanians (Latin: Letwini; Low German: Lettowen; Old East Slavic: Литъва, Литва; Old Swedish: lättugha; modern Lithuanian: rytiniai senlietuviai) were one of the largest East Baltic tribes, inhabiting present-day Eastern Lithuania in the 5th–13th centuries. Following the Northern Crusades, the ancient Lithuanians began gradually assimilating other neighbouring Baltic tribes, becoming the primary progenitor group of modern Lithuanians.

Leo I of Galicia (Old Ruthenian: Левъ Данилович; Ukrainian: Лев Дани́лович, romanized: Lev Danýlovych; Latin: Leo dux Ruthenorum; c. 1228 – c. 1301) was King of Ruthenia, Prince of Belz (1245–1264), Przemyśl, Galicia (1264–1269), and Kiev (1271–1301).

He was a son of King Daniel of Galicia and his first wife, Anna Mstislavna Smolenskaia (daughter of Mstislav Mstislavich the Bold). As his father, Lev was a member of the senior branch of Vladimir II Monomakh descendants.

The Dnieper-Oka language (Eastern Peripheral Baltic, Dnieper-Baltic) is one or several extinct Baltic languages, the existence of which is indicated by toponymic data. It occupied the upper reaches of the Daugava, the basins of the upper Dnieper and Desna, the upper and middle Oka and the Seym. Beginning in the 7th and 8th centuries, the Baltic dialects of the region were replaced by Old East Slavic. The only known subdivision of the Dnieper-Oka language is the Golyad language.

The Ukrainian alphabet (Ukrainian: абе́тка, áзбука, алфа́ві́т, or альфабе́т [1928–1933 spelling and before 1933], romanized: abétka, ázbuka, alfávít, or alʹfabét) is the set of letters used to write Ukrainian, which is the official language of Ukraine. It is one of several national variations of the Cyrillic script. It comes from the Cyrillic script, which was devised in the 9th century for the first Slavic literary language, called Old Slavonic. In the 10th century, Cyrillic script became used in Kievan Rus' to write Old East Slavic, from which the Belarusian, Russian, Rusyn, and Ukrainian alphabets later evolved. The modern Ukrainian alphabet has 33 letters in total: 21 consonants, 1 semivowel, 10 vowels and 1 palatalization sign. Sometimes the apostrophe (') is also included, which has a phonetic meaning and is a mandatory sign in writing, but is not considered as a letter and is not included in the alphabet.

In Ukrainian, it is called українська абетка (tr. ukrainska abetka, IPA: [ʊkrɐˈjinʲsʲkɐ ɐˈbɛtkɐ]), from the initial letters а (tr. a) and б (tr. b); алфавіт (tr. alfavit); or, archaically, азбука (tr. azbuka), from the acrophonic early Cyrillic letter names азъ (tr. az) and буки (tr. buki).

Ruthenian (see also other names) was a written language used from the 14th and the 18th centuries within the East Slavic-speaking regions of the Grand Duchy of Lithuania and later the Polish-Lithuanian Commonwealth. Literary Ruthenian is considered to be a historical precursor to the modern Belarusian and Ukrainian languages (occasionally also to Rusyn), although neither standard language directly continues the Ruthenian written tradition.

Several linguistic issues are debated among linguists: various questions related to classification of literary and vernacular varieties of this language; issues related to meanings and proper uses of various endonymic (native) and exonymic (foreign) glottonyms (names of languages and linguistic varieties); questions on its relation to modern East Slavic languages, and its relation to Old East Slavic (the colloquial language used in Kievan Rus' in the 10th through 13th centuries).

Old East Slavic literature, also known as Old Russian literature, is a collection of literary works of Rus' authors, which includes all the works of ancient Rus' theologians, historians, philosophers, translators, etc., and written in Old East Slavic. It is a general term that unites the common literary heritage of Belarus, Russia, and Ukraine of the ancient period. In terms of genre construction, it has a number of differences from medieval European literature. The greatest influence on the literature of ancient Rus' was exerted by old Polish and old Serbian literature.

Most of the monuments of Old East Slavic literature have been preserved in the form of manuscripts. The most common type of manuscript was literary collections. Notebooks written by a single scribe could then be bound by the scribe or binder himself. Such collections can be of a certain ("Zlatostruy", "Izmaragd", "Solemn", etc.) or indefinite content, reflecting the individual tastes and interests of one or another scribe who selected materials for himself or for his customer.

The Great Troubles (Russian: Великая замятня, romanized: Velikaya zamyatnya, from Old East Slavic замѧтьнѧ, as found in Rus' chronicles), also known as the Golden Horde Dynastic War, was a war of succession in the Golden Horde from 1359 to 1381.

This era, which followed shortly after the Black Death had ravaged the cities of the Golden Horde, was characterised by two decades of near anarchy. A long series of short-reigning khans deposed and killed each other, only to suffer the same fate next. Mamai emerged as the most powerful Mongol warlord, frequently employing Rus' principalities such as Tver and Ryazan as his allies. Because he was not a Chingisid (descendant of Genghis Khan), Mamai had no legitimate claim to the throne, and instead used Chingisid puppet-khans to exercise political control.