Chalcedon addressed another enormous question:
How should Christians speak about the divinity and humanity of Jesus Christ?
The council confessed one and the same Christ in two natures, truly divine and truly human.
Continuity With Earlier Councils
Chalcedon's proceedings explicitly receive the faith of Nicaea and refer to earlier conciliar and patristic authorities.
That reveals something important about ancient Christianity:
doctrinal definition was understood within a received ecclesial tradition.
Primary Source
https://www.newadvent.org/fathers/3811.htm
Division
The reception of Chalcedon became associated with lasting division between Chalcedonian churches and communities now commonly grouped among the Oriental Orthodox Churches.
The history is complex and should not be reduced to "everyone who rejected Chalcedon rejected Christ's divinity or humanity."
Language, terminology, politics and theological interpretation all matter.
Why This Matters
The timeline now shows multiple ancient Christian families before the medieval East-West rupture and long before the Protestant Reformation.
That is why CatholicAgain should never present Christian history as:
Catholic until 1517 → Protestant afterward.
The actual history is richer.