The protracted conflict between the Ottomans and the Safavids was based on territorial and religious differences. Both great empires sought to control vast territories in present-day Iraq, along the Caspian and their mutual borders.
As Sunni Muslims, the Ottoman Empire also disagreed with the Shi’i Safavids over basic religious tenets and practices, similar to the disputes between various Catholic and Protestant powers in Europe.
In 1514, the Ottoman sultan Selim I, father of Suleiman I the Magnificent, declared a holy war against the Safavids, whom he considered heretics. Armed with cannons, the Ottoman army defeated Shah Isma’il, the founder of the Safavid dynasty, and occupied much of northern Persia (present-day Iran).
Suleiman continued the fight against Shah Tahmasp I (reigned 1524–76), but Tahmasp retaliated with a policy of “scorched earth,” making it impossible for the Ottoman forces to live off the land, as was usual for invading armies at the time. Tahmasp also struck an alliance of convenience with the Habsburgs, a major enemy of the Ottomans.
The Ottomans succeeded in taking Tabriz in northern Persia, but, stretched beyond his limits, Suleiman reluctantly signed a treaty with the Safavids in 1555. The Safavids managed to retain control over northern Persia and territory along the Caspian Sea but lost Iraq to the Ottomans. Following Suleiman’s death, Shah Abbas I managed to regain temporary control over Baghdad and Basra in Iraq, but after Abbas died, the Ottomans retook the territories.
The subsequent 1639 peace treaty between the two rival empires established borders that are almost identical to those shared by present-day Iraq and Iran. The two great powers remained enemies but no further warfare broke out.
Over the course of their rivalry, both empires achieved major military victories and suffered military defeats, but neither was able to defeat decisively the other. Their futile warfare undermined the economic and military power of both and was a major factor in their long declines.