And of course the current civil war in Yemen has become a sectarian proxy war, with Iran backing the Shia Houthi rebels who overthrew the country’s Sunni-dominated government, while a Saudi-led coalition has since intervened to reinstall the Sunni leadership.
After four centuries of dominance by powerful intruders (Seljuk Turks, Mongols), Persia acquires in the 16th century a new dynasty from the heartland of the classical Persian empire.
Uzbek tribes, under the leadership of Shaibani Khan, are moving southwest from Samarkand and Bukhara.
By 1507 Shaibani has reached Herat, which he captures in that year.
Another Sunni ruler to the east of Persia is Babur, now established in Kabul.
But Babur has no aggressive intentions against Persia.
The tension is not eased by a Hadith in which the Prophet was quoted as saying: “My Ummah (community) will be fragmented into seventy-three sects and all of them will be in the Hell fire except one.” Inevitably both Sunnis and Shias claim to be the one “pure” Islamic sect. As with any division that lasts over a thousand years, the Sunni-Shia split led to each denomination developing its own unique cultures, doctrines and schools of thought.
His descendants, known from his name as the Safavids, govern the city of Ardabil as a small theocratic state.
In the 15th century they develop a passionate commitment to the Shi'a version of Islam (the family claims descent from one of the twelve Shi'a imams - see The Shi'as).
Only lran, Iraq, Azerbaijan and Bahrain have a Shia majority, although there are also significant Shia populations in Yemen, Lebanon, Kuwait, Syria and Qatar.
Despite being members of the religious minority, the Saudi-backed Kingdom of Bahrain has long been ruled by the Sunni House of Khalifa.