As a result of this successful invasion the Greek Emperor found himself compelled to enter into a treaty with Murad, by which he bound himself to refrain from any attempt to recover what he had lost in Thrace, to abstain from giving aid to the Serbians and Bulgarians in resisting a further advance of the Ottomans in Europe, and to support Murad against his Anatolian enemies, the Turkish Emirs. Murad thereupon returned to Brusa to cogitate over new enterprises and to organize his forces. He was soon recalled to Europe by most serious events. The Christian Powers had shown no disposition to help the Greeks against the Ottoman invasion, while their possessions in Asia and Europe were being invaded, but the advance into Bulgaria seems to have caused alarm to them. Pope Urban V stirred up Louis, the King of Hungary, and the Princes of Serbia, Bosnia, and Wallachia to resist. They combined together and sent an army of twenty thousand men into Thrace, with the avowed object of driving the Turks out of Europe. Murad hastened to confront them, but before he could arrive on the scene of action his general, Lalashahin, led an army against the allies. The two armies met on the River Maritza, not far from Adrianople, in 1363. Ilbeki, in command of the Ottomans, made a sudden night attack, when the Christian troops were heavy with sleep after a festive revel. A stampede took place. The Turkish historian says of the allied army: “They were caught even as wild beasts in their lair. They were driven as flames are driven before the wind, till, plunging into the Maritza, they perished in its waters.” The Christian army was practically exterminated. The King of Hungary escaped by a miracle. It was the first conflict of the Ottomans with the Hungarians, who were destined to bar the way into Europe for a hundred and fifty years. As a result of this battle all the country south of the Balkan Mountains was incorporated in the Ottoman Empire. Ilbeki, who devised the night attack, and so successfully carried it out, was made away with by poison, at the instance of Lalashahin, who was madly jealous of his great victory. The battle of the Maritza was a crushing blow to the Christians. One result of it was that Murad decided in favour of a scheme of conquest in Europe rather than in Asia. In this view he transferred the seat of his government from Brusa to Thrace, and made Demotika the capital of his Empire. Three years later he transferred it to Adrianople, which for ninety years, till after the capture of Constantinople, held this position, and from thence he organized his great invasion of the Balkan States. Another result was that the Greek Emperor, John Palæologus V, was forced into a further step towards subjection to the Ottomans. He agreed to become a tributary to the Sultan and to send a contingent to the Ottoman army in future wars.