This ancient region has been occupied by a variety of peoples including the indigenous nomadic Azeris, as well as Persians, Muslims, Arabs, Turks, Mongols, and Russians. Because of its geographic location, the capital Baku has been important in controlling the Caspian Sea. Though the Persians, Ottomans, and Russians wrestled with each other for hegemony over the area during the 18th and 19th centuries, it was the Russians who eventually gained the upper hand through the Treaty of Turkmenchai (1828), which gave them the northern part of the land. Persia got the southern half. The Russians transformed Azerbaijan into an industrial center. It also became a revolutionary center. Though the first republic established in 1918 was overthrown in 1920 by the Soviet Red Army, a separate Azerbaijan Soviet Socialist Republic did come into being. During the period under Soviet domination, the country underwent industrial growth, collectivization of agriculture, and religious persecution. In 1988, Azerbaijan went to war against neighboring Armenia over the Naborno-Karabakh region (ethnically Armenian, but within Azerbaijan territory). The ensuing hostilities continue. With the fall of the Soviet Union, Azerbaijan has had difficulties with issues of democracy as it tried to hold free and honest elections in 1995 and 1998. Charges of vote-rigging persist and officials sent to monitor the elections of 1998 charged that there were serious irregularities in the process.