"There are two streams of opinion concerning the origin of Iranian Turks. The first maintains that they are the descendants of the Turks who either migrated to Iran in the 7th and 11th centuries or invaded parts of Iran at various times. The second holds that they are original inhabitants of Iran on whom the invaders have imposed their languages throughout centuries of occupation. The Iranian Turks live mainly in the north west of Iran in the Eastern and Western Azarbaijan and Ardebil provinces (capitals Tabriz , Urumiyeh and Ardebil respectively), the Zanjan province up to Qazvin, in and around Hamedan, in Tehran, around Qom and Saveh, Khorasan province, and are scattered throughout many other parts of Iran. Some of the central and southern ethnic groups, the Qashqaie for example, are Turkish speaking .
The Turkish which is spoken in Iran is associated with the Turkish spoken in the Caucasus, but it has undergone varying developments in various regions. The Turkish dialect spoken in both the Azarbaijan province in Iran and in the Republic of Azarbaijan is Oghoz, which is the mother tongue of the Iranian Turks. The Oghoz have two accent groups: the northern and southern. The northern accent is spoken in the Azarbaijan Republic. The southern accent is prevalent in Iran, where the people have been influenced by Farsi. The differences in dialect, and in the culture and customs in particular, among the Turks in Iran has been largely ignored; the emphasis is generally placed on the Turkish language as a whole rather than other characteristics of the Turks in Iran. Several Turkish dynasties have ruled Iran in the past, including the Ghaznavid, Seljuk, Safavids, Qajars. The Turks are thought to be the largest non-Farsi speaking ethnic group in Iran. Back in 1944, a group of left wing nationalists organized the Azarbaijan Democratic Party and established an autonomous government in the Iranian Azarbaijan. They were provided this opportunity by the presence of the Soviet Red Army, who were then a part of the Allied Forces in Iran. During its one-year in office, the nationalist government made Turkish the official language of the region. Upon the withdrawal of the Red Army from Iran, the Iranian army moved in and crushed the rebellion in December 1946."
From: Extract from the Iran Yearbook 1993
In Japan I had a good Iranian friend whose mother tongue was Turkish.