Роман Мстиславич
In the 12th century, a Rurikid Principality of Halych (Halicz, Halics, Galich, Galic) formed there, which merged at the end of the century with the neighbouring Volhynia into the Principality of Halych Volhynia. Galicia and Volhynia had originally been two separate Rurikid principalities, assigned on a rotating basis to younger members of the Kievan dynasty. The line of Prince Roman the Great of Vladimir-in-Volhynia had held the principality of Volhynia, while the line of Yaroslav Osmomysl held the Principality of Halych (later adopted as Galicia). Galicia–Volhynia was created following the death in 1198 or 1199 (and without a recognised heir in the paternal line) of the last Prince of Galicia, Vladimir II Yaroslavich; Roman acquired the Principality of Galicia and united his lands into one state. Roman's successors would mostly use Halych (Galicia) as the designation of their combined kingdom. In Roman's time Galicia–Volhynia's principal cities were Halych and Volodymyr-in-Volhynia. In 1204, Roman captured Kiev, while being in alliance with Poland, he signed a peace treaty with Hungary and established diplomatic relations with the Byzantine Empire.