During the Sultanate of Women ("Kadınlar Saltanatı"), eunuchs increased their political leverage by taking advantage of minor or mentally incompetent sultans. Teenage Sultans were "guided" by regencies formed by the Queen Mother ("Valide Sultan"), the Grand Vizier and the Valide's other supporters – and the Chief Black Eunuch was the Queen Mother's and Chief Consorts' intimate and valued accomplice. Kösem Sultan, mother of Sultan Ibrahim (r. 1640-1648) and grandmother of Sultan Mehmed IV (r. 1648-1687), was killed at the instigation of the mother of Mehmed IV, Turhan Sultan, by harem eunuchs in 1651.