The third council of Constantinople took Chalcedon in a direction that alienated many Churches... and this serious division opened up the weakness that the Islamic armies exploited.
It is tragic that neither Jerusalem nor Alexandria were present at Constantinople III - but were "represented" by Byzantine appointed agents.
Locating "will" in "nature" rather than "person" was always impossible for the African/Arabian/Indian churches - the Churches that were nervous about the language of Chalcedon.
Maximus the Confessor argued that for the Son to be truly human, it was necessary to have a human will as well as a divine will, just as He has a human nature as well as a divine nature.
If the LORD Jesus Christ did not have a human will... then how can He show us how to be human?
How can Jesus model "theosis" if He does not have a human will?
However, for these other Churches from outside the Roman Empire, "will" is associated with the one "person" rather than the two "natures". They argue that Jesus DOES have a fully human will, because the person of Christ is fully human and fully divine.
They agreed that it is essential that the LORD Jesus Christ shows us how to be human, but in the incarnation the PERSON of Jesus is fully human as well as being fully divine... and so His will is also fully human and fully divine in that one person.
The suspicion was that some parts of the one person of Christ were being labelled as human and other parts were being labelled as divine... when surely ALL of Christ, in every part, is fully human and fully divine.
From their perspective, having two wills (a divine & a human) would be like having two consciousnesses (a divine & human) or even two persons (a divine and a human) - and this is the heresy of Nestorianism.
In order to have a full humanity, would Jesus have to have a human "consciousness" or a human "person" in addition to a divine "consciousness" or a divine "person"?
Constantinople II seemed to move away from that kind of thinking.
The proposed solution of Constantinople III only works with a particular anthropology - where a "nature" wills rather than a "person": if a "nature" wills then there must be two wills; if a "person" wills then there can be only one will.
It remains a source of great sadness because the second council of Constantinople had done so well in reassuring the Churches that were nervous about Chalcedon that Chalcedon did not reject them... but Constantinople III went hard against them, without them being present at the Council - and that was especially difficult given that the African & Arabian churches were dealing with Islamic invasions/imperialism.
Today's saint from the Global Church History Project gives us a glimpse into the time of optimism and unity AFTER Constantinople II but BEFORE Constantinople III.
"St. John of Girona lived at a time of optimism for Church unity in the aftermath of Constantinople II.
He begins his chronicle by praising the Emperor Justin II and his symbasileus Tiberius II Constantine for affirming the Council and he goes on to show the fruits of it as peace and respect was finally shared between Christians within and without the Roman Empire.
Immediately after he records:
"The Armenians and Georgians, who received the faith of Christ from the preaching of the apostles, were being compelled by Khosrow the emperor of the Persians to worship idols, but they rejected such an impious order, and so handed themselves over with their provinces to the Romans."
The Chalcedonians had persecuted non-Chalcedonians and thus they stayed in the Persian Empire even when that persecution was ramping up!
Constantinople II made these Christians finally trust the Romans again and they could now stand united against their common foe.
The same was true in Arabia which was facing Persian & Yemeni persecution (note, for example, the Martyrs of Najran):
"al-Mundhir the [Miaphysite] king of the [Ghassanid] Saracens came to Constantinople, and with his wreath and gifts of Barbaria he met the emperor Tiberius. He was kindly received by Tiberius, endowed with lavish gifts, and permitted to go away to his country."
"The ambassadors of the people of the Makuria [a Nubian Miaphysite Kingdom] came to Constantinople: they offered elephant teeth and a giraffe to the emperor Justinus as gifts, and entered into friendship arrangements with the Romans."
No longer fighting with Arab, Persian and African Christians, the Roman Empire was able to help spread the Faith in these areas once again:
"In the third year of Justinus the emperor, the Garamantes made a proposal through envoys, indicating their desire to be joined to the peace of the state and to the Christian faith. They immediately got both things... The people of the Mauritans received the faith in these times."
After Constantinople III, any unity between the Churches of the Roman Empire and the Churches of Arabia, Africa & India was impossible.
I always feel that Constantinople III had an unhappy role in the rise of Islam.
Everybody wanted to strongly affirm that the LORD Jesus Christ is fully divine and fully human as one person - but there was, even down to today, a genuine nervousness that others are failing to do that... either by denying two wills or by affirming two wills!