Moscow's ties with the Islamic Republic of Iran underwent dramatic fluctuations following Ayatollah Ruhollah Khomeini's triumphant return to Tehran in 1979. After a prolonged implosion, they fitfully expanded, shaped not only by the rush of current events but by centuries of ingrained practices and prejudices. By summer 2006, as Iran forged ahead with its nuclear program and Shia-based forces flexed their muscles across the Middle East, Russian-Iranian...