Around 550 BC Persians replaced Medes as the dominant ethnic group in Mesopotamia. Despite conquest by Greeks, Turks and Arabs, Persian language and culture kept re-asserting itself. Afghan Persians are called Tajiks and their dialect of Persian is called Dari. Tajik culture was cemented in Afghanistan by the Samanids, an east Persian empire from 800-1000. One third of Afghans today are Tajiks, and Dari is the language of education and culture in Afghanistan, spoken by half the country.
Persian and Afghan power overlap at Herat, the ancient oasis city, where many Tajiks live. The two kingdoms have fought over Herat many times, but also are also bound together by it. Ismail Khan received support and refuge from Iran during the war against the Soviets. Iran wants Afghanistan peaceful and stable, both out of kinship allegiance, and to reduce the refugee problem. Iran should be our ally in Afghanistan, but we hate them too much.
Just to the east of Herat are the Aimaks, another Afghan-Persian ethnicity, making up about four percent of Afghans. The Hazara in the heart of the country are ethnic Turkic, but they speak a Persian dialect.
The largest population of Tajiks live in the north east, including Kabul, Kondoz, and the Panjishir valley, where Masud built the best organized army in the country. Fahim, Ustad Atta Mohammed, Professor Rabbanni and Yunis Qanooni all come from this Tajik population.
Afghan rulers built the kingdom on the Pashtun tribal militia and Dari speaking administrators. The stereotype of urban, educated Tajiks and wild Pashtun tribesmen remains. Tajik-Pashtun rivalry is dangerous, Masud and Hekmatyar fought along that ethnic fault line. Today Tajiks believe the Pashtun government is plotting against them, while Pashtuns suspect Karzai is selling them out to the Tajiks.