Kievan Rus. 1019 - 1319
The city was first mentioned in historical chronicles in 1019 as Bierascie when Kievan duke Jaroslaw The Wise fought with another duke who was the leader of the slavonic tribe of Dreulane Svyatopolk. Svyatopolk was defeated and escaped to Bierascie which at that time was part of the Duchy of Turau. In 11th century Brzesc was an old Rusian trade center and a fortress on the border with Polish and Lithuanian territories. Located on the islands at the confluence of the rivers Mukhavets and Boog, Bierascie was at the intersection of two trade ways leading through Slavonic lands to Poland, Baltics and Western Europe. One of the ways was going along the Western Bog river from Galicja and Wolyn (currently Western Ukraine). The second way was along Muhawec, Pina, Prypiec, Dniepr rivers connected Brzesc with Kijow the Black Sea and the Middle East.
Because of its border location Brzesc(Brest) often was in the center of military actions it changed hands freequently. In 11-12 centuries the city belonged to Turau and the Galich-Wolyn Duchies. In 1020 Bierascie was occupied by the Polish Duke Boleslaw The Courageous. The Kievan Duke Jaroslaw undertook three attempts to return the city into the Old Russian State, and in 1044 Brzesc finally returned to the Kievan Duchy back to the Old Russian State.
In 1117 Brzesc was subdued by the great Kievan Duke Vladimir Monomakh. Since 1142 the Dukes of the Galich and Valyn headed the city. In the second part of the 12th century Bierascie became the center of the small feudal duchy called Land of Bierascie which was part of Galich-Valyn Duchy. In 1164 the Lithuanian Duke Skirmunt took Bierascie but did not own it for a long time. Unsuccessful were the attempts of the Polish king Kazimierz II in 1179 and 1182 to join Bierascie to Poland.
In 1213 Polish King Leszko occupied Brzesc but in 1222 Wolyn duke Vasilka returned the city to the bosom of the Land of Bierascie. In the beginning of the 13th century the troops of the Polish king Konrad Mazowiecki occupied the city but the population of Brzesc resisted and the king had to return the city to the Galich-Wolyn Duchy. In the middle of the 13th century the Bierascie Land was invaded by Mongols. There is no historical evidence about the depredation of Bierascie by them. Mongols were weakened by fights with Slavonic Duchies and could not move further to Western Europe. Many times Brzesc was besieged by enemies, sometimes the town was burnt down totally but every time it was reconstructed.To defend their territories from invaders the Slavonic dukes built fortification castles and towers. In the 12th century a castle and a fortification to harbour the trade caravans were built in the city. Bierascie served as a customs where the merchants paid their taxes for carrying goods. In 1276 Wolyn duke Wlodzimierz Vasilkovich erected high stone tower in the city. Also he ordered to build up another tower on the Lyasnaya river in Bialowierza Puszcza to defend the northern territories of his duchy. The city of Kamienec soon appeared near the second tower in the primeval forest. The tower in Kamienec still stands as a witness of those events.
To the North of Bierasce, an old Lithuanian-Belarusian state, the Great Duchy of Lithuania, was emerging. The state appeared on the territories of baltic tribes half-assimilated by Slavs. The dukes of Lithuania managed to escape the subjugation to Rusian Dukes and the state was growing and getting stronger. Since the end of the 12th century the Lithuanian territories were attacked by crusaders who wanted to subdue the Baltic and the Rusian territories. To resist the crusaders threat the peace treaty between Rusian and Lithuanian dukes was signed in 1219.