Constantine IV called the Third Council of Constantinople, counted as the Sixth Ecumenical Council by the Orthodox Church, the Catholic Church and some other Christian groups, that met from November of 680 until September of 681 and condemned monoenergism and monothelitism, a doctrine that won widespread support when formulated in 638, as heretical and defined Jesus Christ as having two energies and two wills (divine and human).
With arrival of Islam at the beginning of the 7th century the Byzantine Empire started to lose ground to its enemies in the north (the Avars and Slavs) and in the east (the Sassanians who would soon be supplanted by the Saracens). Those days Emperor Heraclius (610-641) worried that the Monophysite Christians who were isolated from the Western Church might join the eastern enemies of the Byzantine Empire and to find a solution to the disputes between the antagonistic groups a new formula, which skirted the question of natures by claiming that while Christ had “two natures”, as confirmed at Chalcedon he had only a “single will”, was proposed by the efforts of the emperor Heraclius shortly before his death. Although this proposal was accepted by the East, Rome opposed it and consequently it did not achieve the unity that Heraclius had expected.
It was the Emperor Constantine IV (668 - 685) who called the Third Council of Constantinople.
On 7 November 680, a mere 37 bishops and a number of presbyters convened in the imperial palace, in the domed hall called the Trullus. The Patriarchs of Constantinople and of Antioch participated in person, whereas the patriarchates of Alexandria and Jerusalem were represented by Byzantine appointees (because of the Saracen Muslim conquest there was at this date no patriarch in either of these sees). The Pope and a council he had held in Rome were represented (as was normal at eastern ecumenical councils) by a few priests and bishops. In its opening session, the council assumed the authority of an Ecumenical Council. The Emperor attended and presided over the first eleven sessions, took part in the discussions and returned for the closing session on 16 September 681, attended by 151 bishops.
During its 18 sittings, 12 of which were actually led by Constantine IV himself, the council attempted to bring about reconciliation between the Western Church in Rome and the Orthodox Church in Constantinople. The council decreed that Christ had both a divine and human will that matched his two natures, reaffirming the doctrines of the Council of Chalcedon in 451.
This solved the controversy over monothelitism. The council's actions helped to promote a feeling of unity between the two churches and bring them closer together than they had been in recent years.