John had hoped that his adhesion to the Roman Church would bring to him grants of money, ships, and men from the Latin princes, and that an army would rally around him to fight the Osmanlis. But not only did he return from France ‘with empty hands’, but he was detained at Venice because of debts owing to merchants. In vain he begged Andronicus to send the money for his release. The son who had four years before been charged with being party to his father’s imprisonment in Bulgaria was no more filial at this humiliating crisis. He answered that there was no money in the treasury, and that he could get nothing from the clergy. But his younger son, Manuel, brought from Salonika the ransom.[296]
John Palaeologos returned to his capital poorer than when he left. He brought no help from Europe, and he had bound himself publicly by oath to an obligation which he had known he could not fulfil. He had broken faith with Murad, who during these years had been growing more and more powerful. There was nothing for him to do but to make himself tributary to Murad in order that he might enjoy ‘up to the end of his life’ his last possessions in peace.[297] Three years later, in 1373, when his ambassador John Lascaris failed in a second attempt to get aid from the Western princes,[298] the Byzantine emperor recognized Murad as his suzerain, promised to do military service in person in Murad’s army, and gave to him his son Manuel as hostage.[299]
Urban died a few months after John’s visit to Rome. Gregory XI, who succeeded him in December 1370, had little hope of carrying on further negotiations with the Eastern Church; for the Greek ecclesiastics were stubborn in their determination to maintain the absolute independence of the patriarchate. The Genoese and Venetians were fighting bitterly in Cyprus. In 1371, Gregory made a strong appeal to France, England, Venice, and Flanders to co-operate with Genoa in saving the last Christians of the Holy Land.[300] There was no response.
That Gregory realized clearly the peril to Christendom in the advance of Murad’s armies is shown in two remarkable letters written to Louis of Hungary in May and November 1372. His words were prophetic. He urged Louis to resist the Osmanlis before they advanced farther into Europe. They had already entered Serbia. He trembled to think what would happen if they pushed through Albania and secured a port on the Adriatic. Unless Louis entered without delay into an alliance with his Christian neighbours, how could he protect his own kingdom and all Christendom from the Mohammedan peril.[301] Seconding this warning to the King of Hungary, the Pope commanded the Hungarian and Slavic archbishops to preach the crusade in Hungary, Poland, and the Dalmatian cities. Everywhere special boxes were placed in the churches for collecting funds. A tithe was levied on the monasteries and abbeys of Hungary and Dalmatia. Louis, with five of his most powerful nobles, took the cross, and swore to the Pope that he would put an army in the field within a year.[302] Louis asked Venice for triremes, but when the Venetians found that he intended them to be a donation for ‘the common cause’, they found that they could not build them.[303] Padua declined an invitation to guarantee the cost of construction. The Hungarians did not fulfil their promises. In fact, there is no evidence that they made any effort to acquit themselves of their oath.
When John Palaeologos made a last desperate appeal to the Pope, before he entered into his third and final compact with Murad, Gregory, in receiving the imperial envoy, burst into tears, and promised that he would save Constantinople, if only the Byzantine emperor would cause his people to renounce their heresies and return to the Roman Church. In 1375, he wrote once more to Louis to inform him that Constantinople was in danger of capture from Murad.[304] Letters in the same year to Edward of England pictured the Ottoman advance and the peril of Christendom, urged a general war against the Osmanlis, and asked for a subsidy to provide galleys ‘to prevent the crossing into Europe of more Turks, because Constantinople is in imminent danger’.[305] The letters of Gregory XI to the Christian princes prove conclusively that the full import of Murad’s early successes was understood by the Pope and was impressed upon both secular and ecclesiastical authorities throughout Europe.
But both John and Gregory lost heart. Neither was able to fulfil the compact made in Rome. Gregory could not unite Christendom to relieve the Byzantines. John could not persuade the Byzantines to renounce, as he had done, the ‘Greek heresies’. So, as we have seen, he became Murad’s vassal.[306] The Pope, involved in the quarrel of Emperor Charles IV and the Duke of Bavaria with the Marquis of Brandenburg, and anxious over the outcome, for the papacy, of the continual unrest in the Italian cities, returned from Avignon to Rome in 1378. He died a few months later.[307] The struggle arising from the election of Gregory’s successor gave birth to the ‘Great Schism’. This left Murad a free hand in subjugating the Balkan peninsula.
VIII
The sources of information for the movements from the outside for the relief of the Balkan Christians, and for the religious and political quarrels of the Byzantines, are so numerous and so detailed that one is embarrassed by too much material. Many interesting facts cannot even be mentioned. But when we come to the beginning of the Ottoman conquest in Europe under Murad and Bayezid, we find ourselves in the midst of what an eminent Slavic historian has called ‘the most obscure and difficult period of South-Slavic history’.[308] The chroniclers, whether they be Slavic, Rumanian, or Ottoman, are so contradictory and so lacking in explicit statement that we cannot speak with certainty of the sequence of events. The Byzantine chroniclers, verbose to the point of weariness in detailing petty and trifling quarrels and happenings, are almost silent concerning the momentous events that marked the ruin of their empire. It is difficult to unravel the twisted skeins, and find a thread to carry the story of the conquest from 1366 to 1389. When it is impossible to choose between contradictory records, the geography of the field of action, with which one can gain a first-hand knowledge, must be the final factor in determining the sequence of conquest between the adoption of Adrianople by Murad as his capital and the downfall of the Serbians at Kossova.
The occupation of Adrianople and Philippopolis was as severe a blow to the Bulgarians as to the Byzantines. In spite of the fact, however, that Greek and Bulgarian had a common interest in driving the Osmanli from Thrace, or at the very least in checking his advance, there was no move made at this time for an alliance. On the contrary, even when the Osmanlis were engaged in the Thracian campaign, war arose between John V and Alexander. The Byzantines captured Anchiale, and tried desperately to take Mesembria by assault.[309] The Greek patriarch wrote to Czar Alexander, reminding him of the sacredness of harmony and the necessity of accord at that critical moment, but the letter was not backed by the good faith and good will of the Byzantine emperor. Neither John nor Alexander attempted to give assistance to the Serbian and Hungarian crusade that ended so disastrously on the banks of the Maritza.
The conquest of Bulgaria up to the main Balkan range imposed itself upon Murad as a corollary to the Ottoman dominion in Thrace, and the undisturbed possession of Adrianople and Philippopolis. For the Bulgarians, through centuries of varying fortunes, had grown accustomed to fighting for the right to live in Thrace. Often had they been beaten back to the Balkans, and as often pressed forward again to the Ergene. To win and lose Adrianople and other Thracian cities was old history with them. They always came back. Between 1362 and 1365, Murad had experience with Bulgarian persistence and tenacity of purpose. They were masters again of Kirk Kilisse, Midia, Bunar Hissar, and Viza when Murad made his change of capital from Brusa to Adrianople. Yamboli had been strongly fortified by Alexander. Bulgaria seemed as formidable and as forbidding to Murad’s dream of empire as the emirates of Asia Minor.