prince karl of hohenzollern-sigmaringen became the new leader, and was later called prince carol i of romania. while the russo-turkish war was happening, romania battled on the russian side. when the treaty of berlin of 1878 was signed, the great powers made romania an independent state. in return, they had to give russia three of their southern districts of bessarabia. in 1881, the principality became a kingdom, with prince carol ruling as king carol i.