Qazvin (käzvēn´), city (1991 278,826), Tehran prov., NW Iran. A road and rail-transport center, the city has textile and flour mills, and wineries. Qazvin was probably founded by Shapur II, king of Persia, in the 4th cent. AD It was captured by the Arabs in 644. Hasan-i Sabbah, the founder of the secret Ismaili Assassin order, seized (c.1090) the nearby fortress of Alamut and made it the headquarters of the order. Shah Tahmasp I embellished the city with many fine buildings. It was the capital of Persia from 1548 to 1598. In 1722 the city was temporarily captured by the Afghans. During World War I it was occupied by Russian forces. In 1941 the city was bombed by the Soviet air force and after World War II was a stronghold during the brief Soviet occupation of N Iran. The city is also known as Kazvin and Kasbin.