We will now mention the councils of Basel and Florence where, in response to the looming Ottoman threat, the Orthodox and Latin churches attempted to reconcile. The Emperor, in particular, saw this agreement as necessary to ensure survival. 14,15 In order to resist the onslaught of the Ottomans, he required external help, but the Papal forces and the aid of the Latin West would only come through a theological union. The Pope offered his help to the Byzantine Emperor, but only on condition they submit and agree to credal compromise. 16 In light of this hope, a council was called for, first in Basel and later in Ferrara and finally moved to Florence. During the council, three chief doctrinal issues were discussed, the issue of filioque clause, unleavened bread, and papal authority.

XREF: Connects to broader patterns of political-military concerns driving doctrinal compromise in Christian history.

Ali Qureshi, The Fall of Constantinople, loc. 37