Later Crusading and the Ottoman Wars: Papal Campaigns and European Coalitions

The fall of Acre in 1291 ended the last major stronghold of the Latin Crusader states on the mainland of the eastern Mediterranean, but it did not end crusading. Popes and rulers continued to plan expeditions, and some campaigns were formally proclaimed as crusades. In the Balkans, the Ottoman advance prompted coalitions that included the campaigns of Nicopolis in 1396 and Varna in 1443–1444. In the Mediterranean, crusading language later accompanied papally sponsored alliances against Ottoman power.

These campaigns belonged to a wider pattern of warfare. A papal crusade was not simply any war between Christian and Muslim powers: it was formally promoted by the papacy and could offer participants spiritual benefits, including an indulgence, a remission of penance within church teaching. But the kingdoms and republics that fought the Ottomans also had practical aims, such as protecting borders, recovering territory, and safeguarding trade. The history of later crusading is therefore both the history of papally sanctioned campaigns and of the broader Ottoman wars, which did not always have crusade status.

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After Acre: crusading beyond the Holy Land

After 1291, proposals to recover the Holy Land continued, but the large expeditions associated with the earlier crusades did not return. Late medieval campaigns were often smaller, and crusading also developed around other objectives. In 1365, Peter I of Cyprus led an expedition that captured and sacked Alexandria in Egypt. The crusaders withdrew after about a week rather than holding the city or establishing a lasting base.

At the same time, Ottoman expansion brought military pressure closer to the kingdoms of central and eastern Europe. For rulers in the Balkans and Hungary, the immediate questions were how to defend their territories and whether Ottoman advances could be reversed. The papacy could frame a campaign against the Ottomans as a crusade, but it could not by itself resolve the competing priorities of the rulers expected to supply troops, money, and leadership.

Nicopolis and the limits of coalition warfare

In 1396, an international army gathered for a campaign against the Ottomans. Its participants included King Sigismund of Hungary, French and Burgundian nobles, German princes, and the Knights Hospitaller. Venice provided naval support. Pope Boniface IX had proclaimed a crusade against the Ottomans in 1394, during the Western Schism, when rival claimants to the papacy weakened the prospect of unified leadership across Latin Christendom. Philip the Bold, duke of Burgundy, helped sponsor the enterprise, though he did not join the army himself. The coalition brought together participants with different interests: Hungary faced the Ottoman advance directly, while other nobles could seek prestige and military distinction through a crusading expedition.

The allied army reached Nicopolis, now Nikopol in northern Bulgaria, a strongly fortified town on the Danube, and laid siege to it in September. Its position made it an important Ottoman stronghold, but the attackers had not brought the equipment needed for a difficult siege. They expected to take the town or draw its defenders into surrender before a major Ottoman relief force arrived. Sultan Bayezid I instead marched to relieve it, accompanied by the Serbian ruler Stefan Lazarević, an Ottoman vassal.

Command within the coalition was divided. Sigismund urged the French leaders to coordinate their attack with the Hungarian and other allied forces. The French nobles, concerned with honour and the right to lead the battle, pressed ahead. Accounts of the fighting differ, but the French advance appears to have broken through an initial Ottoman line before encountering fresh forces, including cavalry held in reserve. The attackers had become disordered and could not maintain the momentum of their charge. The fighting then spread to the other contingents, and the coalition was routed on 25 September.

The defeat was devastating: many soldiers were killed or captured, and Bayezid ordered the execution of a large number of prisoners. Prominent noble captives, by contrast, could be held for ransom. The army failed to take Nicopolis, and the victory strengthened Ottoman control in the Balkans. It also exposed the difficulty of turning a coalition assembled under crusading auspices into a unified fighting force, particularly when leaders disagreed about command and the conduct of battle.

Varna: a renewed campaign and a broken peace

The Ottoman advance continued to threaten Hungary and the Serbian lands. By 1439, the Ottomans had brought Serbia under their control, and in 1440 Murad II failed to capture Belgrade, a major Hungarian border fortress. Meanwhile, political conflict over the Hungarian crown complicated the kingdom’s response. Władysław III, already king of Poland, was crowned king of Hungary in 1440, while John Hunyadi emerged as a leading military commander responsible for the southern frontier. Hunyadi’s victories against Ottoman forces in 1441 and 1442 helped make a larger campaign seem possible. Đurađ Branković, the Serbian ruler displaced by Ottoman expansion, also supported efforts to recover Serbian territory.

Pope Eugenius IV issued a crusading bull on 1 January 1443. A bull was a formal papal letter; in this case it gave religious sanction to a campaign against the Ottomans. Led by Władysław and Hunyadi, the army advanced into the Balkans in late 1443. It took Nish and reached the region of Sofia, but its progress was checked at Zlatitsa Pass in December, where Ottoman forces held a strong position in severe winter weather. On the retreat, the crusaders ambushed and defeated a pursuing force at Kunovica, capturing a relative of the Ottoman grand vizier. The mixed course of the campaign made it possible for its leaders to present the return as a success, even though the army had not achieved its wider aims.

Negotiations led to the Peace of Szeged, sworn in August 1444. The agreement offered both sides a pause in the fighting, but it did not end the crusading project. Władysław and the papal legate, Cardinal Giuliano Cesarini, supported a renewed campaign, and the coalition again took the field later that year. The decision to resume war after a sworn peace reflected a collision between the military ambitions of the crusade and the obligations created by diplomacy.

The armies met near the Black Sea port of Varna on 10 November 1444. The Ottoman forces, led by Murad II, defeated the coalition. Władysław disappeared during the battle and was presumed dead, although his body was not recovered and later accounts of his fate differed. Cesarini was also killed. The defeat ended this major attempt to push the Ottomans back from the Balkans. It did not stop Ottoman expansion: after another victory at Kosovo in 1448, the Ottomans took Constantinople in 1453. The defeats weakened efforts to relieve Byzantine pressure before Constantinople fell. Its capture then prompted fresh papal appeals for an expedition.

Mediterranean plans and the Holy League

The fall of Constantinople renewed calls for a crusade. At the Council of Mantua, Pope Pius II promoted an expedition to recover the city, and European leaders promised a large force. Their commitments were not fulfilled. The episode illustrates the gap between a papal appeal and the political cooperation, military resources, and sustained funding that a campaign required.

In the sixteenth century, crusading language became part of a different kind of effort against the Ottomans. In 1571, Pope Pius V helped form the Holy League, an alliance chiefly of the Spanish monarchy, Venice and the Papal States, supported by Genoese, Hospitaller and other Italian contingents. Its members agreed to contribute forces for joint action. The League aimed to resist Ottoman power in the eastern Mediterranean, but it was formed too late to prevent the Ottoman conquest of Cyprus.

On 7 October 1571, the League’s fleet defeated the Ottoman fleet at Lepanto. The victory was striking, but it did not undo the loss of Cyprus or bring the League lasting control of the eastern Mediterranean. Its members had different strategic priorities, and the alliance weakened after Pius V died in 1572. Venice negotiated separately with the Ottomans; peace in 1573 ended the League, while Cyprus remained under Ottoman rule. Spain’s later capture of Tunis in 1573 also proved temporary, as the Ottomans recovered the city the following year.

Crusading language and the wider Ottoman wars

Nicopolis, Varna, and the Holy League show how crusading institutions and language could be applied to wars against Ottoman expansion. Papal authorization distinguished these campaigns as crusades, while the participation of rulers and communities depended on calculations about security, territory, trade, and political advantage. Their religious framing did not erase those interests, nor did it ensure that allies would agree on command, strategy, or the terms of peace.

Not every war against the Ottomans was a crusade. The Ottoman wars were a broader and continuing series of conflicts involving states with changing alliances and aims. Popes continued to sponsor crusades and Holy Leagues against Ottoman power into the seventeenth century, but the language of crusade was increasingly one element within diplomacy and coalition warfare rather than a guarantee of a unified expedition to recover the Holy Land.