The crusaders are hoping for assistance from Emperor John V Palaiologos, but the pope has made it dependent on his bringing the Greek Orthodox Church back into communion with the Roman Catholic Church—and under papal supremacy—even though it is the Constantinople and its empire that the crusade is seeking to relieve from Turkish pressure.

The crusaders also expect support from Louis of Hungary, although all that will ever be received is two royal squires who will serve Amadeus "in the Bulgarian provinces" (in partibus Burgarie).

John V travels in the spring of 1366 to the Hungarian court to accept military aid and swear an oath on behalf of himself and his sons to convert to Catholicism.

Pope Urban had extended to Louis the Crusade indulgence on July 1, but on July 22 a letter from the pope had suspended the privileges granted earlier that month for one year, postponing assistance to the Greeks until after their return to the Catholic fold and convincing Louis not to assist the "schismatic", although the pope had not expressly forbid him to.

On his return through Bulgaria, so recently attacked by his would-be ally, John finds himself trapped, either imprisoned or surrounded by Bulgarian forces, and unable to continue to his own domain, where his son, Andronikos IV, married to Keratsa, daughter of the Bulgarian tsar, has taken control of the government.

Amadeus and John V are first cousins; John's mother, Anna, is the sister of Amadeus's father, Aymon.

After being apprised of the situation in Bulgaria and of the Turkish positions in Europe, Amadeus leads his fleet into the Dardanelles, where it is joined by a flotilla under Francesco I Gattilusio, Prince of Lesbos, and son-in-law of the trapped emperor.

They may also have been met by a detachment of the imperial army under the Patriarch of Constantinople, as the Savoyard chronicles record.

The combined crusader fleet launches an attack on Gelibolu (Gallipoli), the second city of the European Turks, on August 22.

While the army begins the siege with an assault on the walls, during the night the Turks abandon the city and in the morning the inhabitants open the gates to the crusaders.

The sources shed limited light on this brief episode.

It is known from the count's register that both town and citadel are in Savoyard hands by August 26, and garrisons and commanders are appointed for each—Giacomo di Luserna for the city and Aimone Michaele for the citadel, with responsibility for not just defending Gelibolu but also for guarding the entrance to the straits.

On August 27, a messenger is sent westward with news of the count's victory.