The Safavid era peaked in the reign of Abbas I (1587–1629), surpassing their Turkish archrivals in strength, and making Iran a leading science and art hub in western Eurasia. The Safavid era saw the start of mass integration from Caucasian populations into new layers of the society of Iran, as well as mass resettlement of them within the heartlands of Iran, playing a pivotal role in the history of Iran for centuries onwards. Following a gradual decline in the late 1600s and the early 1700s, which was caused by internal conflicts, the continuous wars with the Ottomans, and the foreign interference (most notably the Russian interference), the Safavid rule was ended by the Pashtun rebels who besieged Isfahan and defeated Sultan Husayn in 1722.