After the disintegration of the Old Rus state in the 12th century into separate regional formations, the Halytsian-Volynian principality had undertaken the state-creating traditions of Rus. In spite of the devastating wars, which had not passed through the principality, certain stabilization of economic and political development was observed in this area in the 12th century. The increase in population, economic potential, as well as the regulation of economic relations was visible in the Halytsian Subcarpathia and Volyn territories. In 1199, principalities with common economic and cultural conditions and political and economic relations, united and formed the Halytsian-Volynian state under the reign of Halytsian Prince Roman, a descendant of Volodymyr Monomakh. Prince Roman was the first in the history of the Old Rus state to be referred to as "Grand Duke", "Autocrat of the whole Rus".
The reinforcement of the Prince's power in the Halytsian-Volynian state took place under constant hostility on the part of the powerful boyar opposition supported by foreign protectors: Hungarians and Poles. After the death of Roman Mstyslavych, the boyars succeeded in excommunicating his sons: Danylo and Vasylko. In 1214, Kalman, a young Hungarian prince who married a Polish Princess, was proclaimed King of the Halytsian-Volynian principality. From that time began a long war by Danylo Halytskyi and his brother Vasylko to have their father's throne returned to them. This war became known as the liberating war, for restoring state independence and territorial unity of the Halytsian-Volynian principality. Danylo Romanovych's main task was to reinforce the state institutions of the principality and social support, which the boyars should have returned to him. Under these conditions, he allowed for the state-creating experience of Byzanthia and a number of other West European countries.
By the end of the 1230s, Danylo Halytskyi managed to secure the neighborly relations by marrying his son to the daughter of Bela IX, the Hungarian King. The Prince had rendered great services to his country in protecting boundaries of the Halytsian-Volynian Principality during the Mongol-Tatar invasion to Rus. The fortification line he had constructed immediately before the invasion allowed decreasing the number of plundering raids as compared to other principalities. For 1254-1255, he succeeded in gaining a number of victories over the Horde armies and in driving them away - outside the boundaries of Ukraine.
The internal and foreign policy of Danylo Halytskyi favored the increase of
his popularity in the eyes of the world community. Courtiers of European
countries considered it an honor to be associated with the Halytsian-Volynian
Prince. In 1253, he was crowned by Pope Innokentyi IX in the town of Dorohychyn,
in Pidliashia. This act confirmed the recognition of the Halytsian-Volynian
principality as a subject of international law. Territorial possessions
of the principality considerably increased in the 13th century, under
the descendant of Danylo Romanovych. In particular, the lands of Liublin
and a part of Transcarpathia were added to the principality. The Halytsian-Volynian
Prince possessed the lands of Lithuania for a certain time. Notwithstanding,
the partial economic and political dependence on the Golden Horde, the
Principality leaders managed to keep to their own foreign policy. But
the constant exhausting struggle with foreign and home enemies gradually
weakened the Halytsian-Volynian principality, of which its enemies took
advantage without delay. At the end of the 14th century, the lands of
the recently strong state proved to be divided between Poland, Lithuania,
Hungary and Moldavia.