In 1976, Dinkha IV was elected as Shimun XXI Eshai's successor. The 33-year-old Dinkha had previously been Metropolitan of Tehran, and operated his see there until the Iran–Iraq War of 1980–1988. Thereafter, Dinkha IV went into exile in the United States and transferred the Patriarchal See to Chicago. Much of his patriarchate had been concerned with tending to the Assyrian–Chaldean–Syriac diaspora community and with ecumenical efforts to strengthen relations with other churches. On 26 March 2015, Dinkha IV died in the United States, leaving the Assyrian Church of the East in a period of "sede vacante" until 18 September 2015. During that time, Aprem Mooken served as the custodian of the Patriarchate of Seleucia-Ctesiphon.