During the first half of the fifteenth century Europe, although shaken by the Great Schism and deeply divided by wars, had one obvious enemy: the Ottoman Turk, who professed a different religion and, for this reason, was not just an enemy but the enemy of Christ and of the Cross. This fact did not prevent a Christian state from pursuing commercial relations with the Turks, or even from appealing to them for help against another Christian state. However, in religious propaganda and political theory it was the Turk who was labelled as the eternal foe.
The process of Ottoman expansion was halted by the Anatolian campaign of the Mongol khan, Timur. The Christians had watched his movements with great interest at least since 1394, when his troops began to press the eastern frontier of the Ottoman lands. The whole Christian world felt deep relief when the Mongol army dissolved the Ottoman state by crushing Sultan Bayazid I’s troops near Ankara and taking him prisoner (1402). Timur, with his army, stayed in Anatolia for approximately one year after his victory. Towns and countryside were laid waste and the population, Muslim and non-Muslim, was mercilessly massacred by the Mongols. Crowds from Anatolia swarmed into the Balkans to save their lives and Constantinople was thronged with refugees. Nevertheless, the Byzantines kept celebrating the victory of Timur as if he were sent by God to liberate their besieged capital and to allow their state to grow and survive. Western Europeans, liberated from the danger of the Ottoman threat, tried to confirm their old commercial privileges in the Levant, but they did not proceed openly to further destruction of Ottoman power because conflicts among them were soon to break out.
The Ottoman Empire disintegrated in Anatolia as the various Turkish states, which had been annexed by the Ottomans, were restored by Timur to their previous lords (emirs). Once again Anatolia became a mosaic of small states: the emirate of Sarukhan having Manisa as its capital; the emirate of Germiyan, in the alum-producing region of Kutahya; the emirate of Aydin with the important towns of Smyrna and Ayasoluk (Ephesus); the emirate of Menteshe in the fertile plain of the Meander, with Balat (Miletus) as its capital; the emirate of Isfendiyar in the copper-producing region of Sinope. This last, which maintained frequent relations with the states situated on the northern Black Sea coast and in the mouth of the Danube, would play an important role in further political developments. In the European provinces (Rumelia) the Ottomans very soon recovered and started defending their possessions.
The earlier situation explains these developments. The Ottoman state, which had originated in Bithynia and had Bursa as its capital, represented a most important difference from the other Turkish emirates which had emerged in Anatolia after the collapse of the Seldjuks (c. 1300). From 1354 onwards, it expanded into the Balkans by conquering Byzantine and Slav territories and a second, European capital, Edirne (Adrianople), was created. The conquest in Europe, accomplished in the name of holy war (jihad) against the infidel, which was dictated by the Koran and constituted the official ideology of the state, attributed wealth and prestige to the sultans, who then turned to the east and, after negotiations or war, were gradually able to annex the other Turkish states and transform them into provinces (sanjaks) of their realm.
Only the emirate of Karaman resisted successfully. The house of Karaman, like that of Osman, claimed affiliation with the Seldjuk sultans of Anatolia, because both houses wished to appear as their legitimate successors. The Karamanoglus possessed the Seldjuk capital, Konya (Ikonion), and carried out holy war against the neighbouring Christian kingdom of Cilician Armenia until the latter vanished in 1375; they also maintained political contacts with the Mamluks of Egypt and Syria, and commercial relations with the Franks of Cyprus. By the end of the fourteenth century Karaman was in a weak position resulting from Ottoman pressure, but it recovered after the invasion of Timur, who favoured it particularly.
The situation was different in Rumelia, the land where holy war was carried out against the Christians. In addition to the provinces of the state and the territories ruled by the sultan’s Christian vassals, there were the domains of the lords of the marches, the udj beys, that is the semi-independent military commanders entrusted by the sultan with conquest. Those among them who had long been established in Rumelia possessed redoubtable power. The most representative uj bey of those years is Evrenos, lord of the region around Thessalonica. Another enterprising udj bey of the time was Pasha-Yigit, established in Skopia. The presence of the uj bey resulted in the efficient military organisation of Rumelia which was not affected by the defeat at Ankara.
Although some Christian vassals of the sultan tried to take advantage of the situation, the Ottomans were able to keep them under control. Furthermore, Turkish military manpower in Rumelia was to be reinforced after the defeat. Bayazid’s elder son, Suleyman, had abandoned the battlefield of Ankara when a Mongol victory became evident, and marched westwards to the Straits. He was accompanied by his father’s vizier, Ali Djandarlt, descendant of a noble family whose members took over the vizierate in a hereditary way. Fearing the Mongols, numerous cadres of the Ottoman state and whole contingents of the army managed to cross the Straits, in spite of a Christian plan, disregarded by greedy Genoese and Venetian sailors, that no Turk should be transported to the European side.
Three sons of Bayazid, Suleyman, Mehemmed and Isa, staked an immediate claim to leadership over the Ottomans after their father’s defeat. The Christian states, particularly the Byzantines, the Venetians and the Wallachians, tried to secure maximum advantage from the division of the Ottomans by supporting one prince against the others. Among the Turks, the idea that there was a family singled out by God to rule over them was deeply rooted. For the Ottomans, this was the family of Osman, only one of whose members was destined to become sultan. This conviction resulted in the custom of fratricide according to which a new sultan had to put to death his brothers or any other possible candidate to the throne. The custom, attested to exist in the middle of the fourteenth century, was to become a law, officially decreed by Mehemmed II after the fall of Constantinople. However, in the crucial period following the battle of Ankara, this conviction contributed considerably to the reunification of the Ottoman state. It is remarkable that none of the udj beys or high officials disputed the throne or tried to establish his own rule. The only separatist movement, that of Djuneyd in the region of Smyrna, took place under the cover of members of the sultanic family.
Despite the strong position of the Ottomans in Rumelia, Suleyman, established in Edirne, yet afraid of a possible crossing of the Mongol army, began to solicit the Byzantine emperor and the other Christian powers of the Levant for peace. He knew, furthermore, that he would have to fight his brothers, particularly Mehemmed, for the throne. Rumours had certainly reached him that Mehemmed, established in the region of Amasya, where he had resided before the Mongol invasion, recognised Timur as his overlord.
After fairly long negotiations Suleyman concluded a peace treaty with the Christian powers of Romania, namely the Byzantine emperor, the Knights Hospitallers of Rhodes, Venice, Genoa and the duke of Naxos; the ruler of Serbia and the marquis of Bodonitza were also included (February 1403).
According to the main clauses of the treaty, the Byzantines took back an important territory in Thrace extending from the Propontis up to the Black Sea, as well as Thessalonica with its region; furthermore, they were exempted from all tributes formerly paid to the sultan. The Genoese colonies of the Levant and the duke of Naxos were also exempted from tributes. The Venetians resumed all their territories which had been conquered by the Ottomans in the past, and were granted a few new ones. The Hospitallers of Rhodes were to receive Salona in the Gulf of Corinth. Apart from these concessions, and other minor ones, made to each party separately, Suleyman reconfirmed old commercial privileges and guaranteed the safe-conduct of trade within his lands. Evrenos and other Turkish notables were very displeased at Suleyman’s concessions to the Christians. In some cases, the Turkish authorities openly displayed their disapproval of the treaty: when Byzantine officials went to take over Thessalonica, they met with the resistance of the Turks who rallied on the citadel and occupied it for a while until they received new orders to surrender.