The modern Republic of Azerbaijan lies in the eastern Caucasian region along the western shore of the Caspian Sea, a point of contact between world powers. The area has been under varying degrees of foreign rule for much of its history. From the 16th to 18th centuries, what is today Azerbaijan was under the control of the Safavid dynasty of Persia, leading to the conversion of the formerly Sunni area to Shi'ite Islam. In the early 19th century, much of the southern Caucuses were incorporated into the expanding Russian Empire at the expense of Ottoman and Iranian territory. After the collapse of the tsardom during WWI, Azerbaijan achieved independence for a brief period before being reconquered by Soviet Russia in 1920. The late Soviet period saw a rise of localized violence in the region, as in many parts of the USSR, culminating in a war fought between Azerbaijan and Armenia over the former's separatist province of Nagorno-Karabakh, which continued after the 1991 collapse of the Soviet Union. Although hostilities between the two states ceased in 1994, tensions remain. Today, independent Azerbaijan enjoys a status as one of the wealthiest countries in the region, with a thriving energy and international trade sector.