Turks mostly subscribe to the Hanefi school of Sunni Islam, while
Iran is predominantly Shiite. That is, even though both countries have
predominantly Muslim populations, religion wise they have very little
in common except the holy book Koran and fundamental elements of Muslim
culture. Perhaps due to the shaman past of the Turks or the intense
centuries long cultural interaction with the West, particularly with
France, and to a large extent, thanks to the pre-Turkish culture of
Anatolia, even the Sunni Islam perception of Turks is far different and
incredibly tolerant compared to Sunni practice elsewhere.
Though continued animosities between the Turks and the Iranians came
to an end with the landmark Kasr-i Şirin peace treaty in 1639 (the
Turkish-Iranian border has remained intact since then), ever since,
state-to-state relations between the two remained “cordial.”
Pahlavi, who would have been Iran’s shah today if the Islamic
revolution did not dethrone his father, said that Turks must be aware
of the importance of secularism because without it the country cannot
sustain its democracy. He was in a way admitting that the shah regime
came to an end because it could not sufficiently enforce secularism and
in the hopes of sustaining the regime allowed the advance of Shiite
theocracy.