 The city would subsequently remain in Safavid hands until its fall in 1736.In 1651, Safavid troops clashed with those of the Tsardom of Russia in the North Caucasus, known as the Russo-Persian War of 1651-1653.The main issue involved the expansion of a Russian garrison on the Koy Su River, as well as the construction of several new fortresses, in particular the one built on the Iranian side of the Terek River.