Albania, an ancient country in the Caucasus, was turned into a Sasanian province by Šāpūr I (c. 253). The Albanians became increasingly integrated into the battle order of the Iranian army (especially cavalry). All along the Caspian coast the Sasanians built powerful defense works, designed to bar the way to invaders from the north. The most celebrated of these fortifications are those of Darband in Caucasian Albania. Albania remained an integral part of the Sasanian Empire until the Arab conquest of Iran.