During his brief majority reign, Murad IV (1612–1640) reasserted central authority and recaptured Iraq (1639) from the Safavids. The resulting Treaty of Zuhab of that same year decisively parted the Caucasus and adjacent regions between the two neighbouring empires as it had already been defined in the 1555 Peace of Amasya. The Sultanate of women (1648–1656) was a period in which the mothers of young sultans exercised power on behalf of their sons. The most prominent women of this period were Kösem Sultan and her daughter-in-law Turhan Hatice, whose political rivalry culminated in Kösem's murder in 1651. During the Köprülü Era (1656–1703), effective control of the Empire was exercised by a sequence of Grand Viziers from the Köprülü family. The Köprülü Vizierate saw renewed military success with authority restored in Transylvania, the conquest of Crete completed in 1669, and expansion into Polish southern Ukraine, with the strongholds of Khotyn and Kamianets-Podilskyi and the territory of Podolia ceding to Ottoman control in 1676.