In ancient times, nomad tribes of the north Caucasus, passing through Caucasian natural gates, most importantly among them, Darial and Derbent, plundered wealthy southern regions. During of reign of Khosrow Anushirvan, the Sasanian king built strong fortresses along these passages, and Caucasian nomadic tribes of the north Caucasus could no longer pass through these two passages to invade southern regions.In this paper, according to all the historical sources, including Caucasian, Roman and Iranian-Islamic sources, we try to show how, in the 6th century AD, the nomad tribes who were no longer able to penetrate through the two former passages, turned their attention to Lazica as third major Caucasian passage. We will study how the Iranians and the Byzantines attempted to dominate this passage by war and diplomacy.