The 451 Council of Chalcedon caused problems for the Armenian Church which formally broke off communion with the Chalcedonian Churches at the 3rd Synod of Dvin in 610, some Armenian bishops and congregations made attempts to restore communion with the Chalcedonian Churches after the 6th Ecumenical Council of 681. During the Crusades, the Church of the Armenian kingdom of Cilicia entered into a union with the Catholic Church, an attempt that did not last. The union was later re-established during the Council of Florence in 1439, but did not have any real effects for centuries.