Persian culture and Shi’ism held Iran’s ethnic periphery together after the Safavids

Evidence

The Safavids for the first time created a united realm of Iran, more or less within its present frontiers—not just diverse regions, Pars and Khurasan and the rest of them, but a single realm with a single ruler. It has remained so ever since, in spite of the immense ethnic diversity which characterizes that country to the present day. If you look, for example, round the periphery, starting in the north-west, you have the Turkish-speaking Azarbaijanis. To the south of them are Kurds, to the south of them are more Turks, the Qashqais, to the south of them, in Khuzistan are Arabs, in the south­ east the Baluchis and then the Turkmen. These form a periphery, all around the center, of peoples speaking different non-Persian languages. Nevertheless, the culture of the Persian language and the distinctive Shi‘ite version of Islam helped to maintain the unity that was imposed by the Safavids and maintained by their successors. — Bernard Lewis, From Babel to Dragomans, 305