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How do you conduct diplomacy that is in principle prohibited with a new and technically hostile power? This was the question that guided Andrea Raffaele Aquino’s initial research for his doctoral dissertation on the relations between the Republic of Florence and the Ottoman Sultanate between the fall of Constantinople (1453) and the fall of Negroponte (1470). Aquino is a postdoctoral fellow at the Sapienza University of Rome, where he also obtained his PhD in early 2025 within a cotutelle programme with the University of Granada. He explored the same issue on 9 March 2026, during the last session of the DiplomatiCon Seminars series, with a presentation titled The Ottoman Levant: a Testing Ground for Florentine Diplomacy (1453-1470).

The fall of Constantinople had reshuffled the commercial map of the eastern Mediterranean, and Florence moved fast to fill the gap. But formal engagement with the Sultan was politically impossible: the papacy was organizing a crusade, and Florence could not be seen striking deals with the infidel. Venice had done exactly that in 1454 and was loudly condemned, especially from Rome. Official embassies were out of the question, and yet, Florence kept diplomatic ties with the Ottomans throughout the 1460s.

Aquino’s answer to the initial question lies in four overlapping diplomatic channels, often intertwined, sometimes in conflict. These categories are analytical tools used to frame complex realities. Institutional diplomacy is documented through letters from the Florentine Signoria to Mehmed II (d. 1481). Concise and formal, the letters focus on commercial matters, with galley captains occasionally acting as diplomatic envoys.

Medicean diplomacy ran alongside it: Cosimo de’ Medici (d. 1464) personally managed the Levantine issue through private agents and commercial correspondents, sometimes bypassing public offices entirely. Medicean diplomacy ran parallel to the institutional one and had the objectives of strengthening the family’s commercial interests in the East, improving Florentine trade with Constantinople, as well as leveraging the Levantine situation to pursue his Italian policy.

Then there was frontier diplomacy, that is the activity of Florentine merchants in Ottoman territory who had no mandate, but whom Mehmed II nonetheless treated as representative of the authority of Florence. Aquino cited as the most famous example Benedetto Dei, a man of many talents: a merchant, a traveller, an informant for the Medici. Dei, in his letters and other writings, claimed to have been very close to the Sultan, even as his adviser and his ambassador to Cairo. Dei was not the only one, other merchants were apparently close to the Sultan, and the primary objective of these border, or frontier, actors was to preserve their lives and businesses.

Lastly, between all these elements, there was also the consular diplomacy. The consul’s main task was to represent the Florentine community and administer justice within it. However, since no official ambassadors were sent until 1488, the consul ended up performing several roles at the same time: he was expected to represent simultaneously the merchant community, the Florentine Republic and the Medici who had appointed him; transmit information; and interact with the Sultan.

The discussion that followed Aquino’s presentation brought in a comparative perspective from Alessandro Rizzo, who is a postdoc at the University of Barcelona, where he is conducting research on the relationships between the Crown of Aragon and Muslim powers, and whose research interests comprise relations between Florence and the Mamluk Sultanate in the same period. Rizzo highlighted two distinctive features of the Florentine case. First, its relative lateness in building such practices compared to Genoa or Venice, and the interest in the progressive institutionalisation of these frameworks. Second, the two-tiered nature of Florentine power: the official power of the Signoria and the authority of the Medici, which intersected but did not always align, a fact that other powers did not always read the same way. A Mamluk envoy visiting Florence in the 1480s, Rizzo noted, brought separate gifts for the Signoria and for Lorenzo de’ Medici, delivered on separate occasions. Rizzo also questioned Aquino on versatile figures like Benedetto Dei, who claimed to have served as Mehmed II’s envoy to Cairo, a mission Aquino suspects was invented to sell himself to the Medici as indispensable.

The whole enterprise of Florentine Levant diplomacy, Aquino concluded, was shaped by fear: of destabilisation in the Eastern Mediterranean that might endanger merchant lives and investments, of Venetian dominance in Italy, of an Ottoman invasion that could disrupt the established balance of power favoured by Florence. The diplomatic system developed by Florence for managing relations with Ottoman Constantinople was experimental, fragile, giving its agents a sense of precarity. In this diplomatic system information was the most valuable commodity in circulation, enabling individuals to attain positions of influence and as advisors close to the Sultan, as informants for the Medici, or as merchants able to seize opportunities in a rapidly changing environment.