Complex sentence: The northeastern segment of the high plateau of Eastern Anatolia converges with the Lesser Caucasus mountain range in the region of Kars and Ardahan, which from 1878 until 1917 were incorporated into the Russian Empire region of Transcaucasia as the militarily administered march province of Kars Oblast.
Split into simpler sentences: The northeastern segment of the high plateau of Eastern Anatolia converges with the Lesser Caucasus mountain range in the region of Kars and Ardahan. From 1878 until 1917 these provinces were incorporated into the Russian Empire region of Transcaucasia as the militarily administered march province of Kars Oblast.