Palaeologus granted possession of the island of Tenedos to the republic. The island commanded the entrance to the Dardanelles.
At the capture of Constantinople by the Turks (1453) he fell into their hands, but managed to escape to Peloponnesus, where he obtained protection at the court of Thomas Palaeologus, despot of Achaea.
Michael Palaeologus had actually appealed to Louis IX.
In 1274, at the council of Lyons, Gregory X., who had been the companion of Edward in the Holy Land, preached the Crusade to an assembly which contained envoys from the Mongol khan and Michael Palaeologus as well as from many western princes.
The emperor John Palaeologus, pressed hard by the Turks, showed a great desire to unite himself with the Catholics; he consented to come with the principal representatives of the Greek church to some place in the west where the union could be concluded in the presence of the pope and of the Latin council.