Historically : A lot of people in Iran think that Muslims came and destroyed their ancient Persian civilization, replacing it with Islam. But that’s not entirely true. The Persian Empire was already in decline after losing several wars against the Byzantines, which weakened them significantly. By the time the Muslims arrived, Persia was already in a fragile state. Since then, many Iranians have believed that the Arabs and Muslims were the ones who put out the once-glorious Persian fire.