Rus' principalities in the context of "Great Troubles"

Andrew II (Hungarian: II. András, Croatian: Andrija II., Slovak: Ondrej II., Ukrainian: Андрій II; c. 1177 – 21 September 1235), also known as Andrew of Jerusalem, was King of Hungary and Croatia between 1205 and 1235. He ruled the Principality of Halych from 1188 until 1189/1190, and again between 1208/1209 and 1210. He was the younger son of Béla III of Hungary, who entrusted him with the administration of the newly conquered Principality of Halych in 1188. Andrew's rule was unpopular, and the boyars (or noblemen) expelled him. Béla III willed property and money to Andrew, obliging him to lead a crusade to the Holy Land. Instead, Andrew forced his elder brother, King Emeric of Hungary, to cede Croatia and Dalmatia as an appanage to him in 1197. The following year, Andrew occupied Hum.

Although Andrew did not stop conspiring against Emeric, the dying king made Andrew guardian of his son, Ladislaus III, in 1204. After the premature death of Ladislaus, Andrew ascended the throne in 1205. According to historian László Kontler, "[i]t was amidst the socio-political turmoil during [Andrew's] reign that the relations, arrangements, institutional framework and social categories that arose under Stephen I, started to disintegrate in the higher echelons of society" in Hungary. Andrew introduced a new grants policy, the so-called "new institutions", giving away money and royal estates to his partisans despite the loss of royal revenues. He was the first Hungarian monarch to adopt the title of "King of Halych and Lodomeria". He waged at least a dozen wars to seize the two Rus' principalities, but was repelled by the local boyars and neighboring princes. He participated in the Fifth Crusade to the Holy Land in 1217–1218, but the crusade was a failure.

The gathering of the Russian lands or Rus' lands (Russian: собирание русских земель) was the process in which new states – usually the Principality of Moscow and the Grand Duchy of Lithuania – acquired former territories of Kievan Rus' from the 14th century onwards, claiming to be its legitimate successor. In Russian historiography, this phenomenon represented the consolidation of a national state centered on Moscow. The sobriquet gatherer of the Russian lands or Rus' Land (Russian: собиратель русской земли, romanized: sobiratel' russkoi zemli) is also given to the grand princes of Moscow by Russian historians, especially to Ivan III. The term is also used to describe the expansion of the Grand Duchy of Lithuania into Rus' principalities; the Lithuanian grand dukes claimed authority over all territories inhabited by Rus' people (East Slavs). Some historians argue that Lithuania began "gathering Rus' lands" before Muscovy did. The rulers of Moscow adopted the title Sovereign of all Russia (later changed to Tsar of all Russia and finally Emperor and Autocrat of all Russia) while the Lithuanian Grand Dukes adopted the title King of the Lithuanians and [many] Ruthenians and later under the Polish–Lithuanian union as King of Poland, Grand Prince of Lithuania, Rus, Prussia, Samogitia, Mazovia and other.

The Laurentian Codex or Laurentian Letopis (Russian: Лаврентьевский список, Лаврентьевская летопись) is a collection of chronicles that includes the oldest extant version of the Primary Chronicle and its continuations, mostly relating the events of the northeastern Rus' principalities of Vladimir-Suzdal.

Kievan Rus' law or law of Kievan Rus', also known as old Russian law or early Russian law, was a legal system in Kievan Rus' (since the 9th century), in later Rus' principalities, and in the Grand Duchy of Lithuania from the 13th century. Its main sources were early Slavic customary law and Zakon Russkiy (Law of Rus'), which was partly recorded in Rus'–Byzantine Treaties. A number of articles have similarities with the Germanic (barbarian) laws, for example, the "Salic law" – a collection of legislative acts of Francia, the oldest text of which dates back to the beginning of the 6th century. The main written sources were Russkaya Pravda ("Rus' Justice") (since the 11th century) and Statutes of Lithuania (since the 16th century).

The Olgovichi or Olhovychi were one of the four dominant princely clans of Kievan Rus' in the 12th and 13th century. First mentioned in the Hypatian continuation of the Primary Chronicle (PVL) under the year 1116 and literally meaning "the sons of Oleg", they were named after Oleg I Sviatoslavich, Prince of Chernigov (r. 1094–1097) and Principality of Novgorod-Seversk (r. 1097–1115). He was the grandson of Yaroslav the Wise; ruling dynasty in the Chernigov principality, Novgorod-Seversky principality, as well as with interruptions: in the Kiev, Galicia, Volyn, Pereyaslav principalities, Novgorod lands.