In 1349 Cantacuzenos called again upon Orkhan to send soldiers to him in Europe. Twenty thousand Ottoman cavaliers, under the command of Matthew, marched against Salonika, which was on the point of giving itself to Stephen Dushan. Cantacuzenos, with the young emperor John, went by sea. Orkhan, as on the last occasion, secretly worked against his father-in-law. After Cantacuzenos had already sailed, he recalled the horsemen who were with Matthew. It was fortunate for Cantacuzenos that he met at Amphipolis a Turkish fleet which was about to land a force of raiders to ravage the country, and persuaded the commander to join with him in a demonstration against Salonika. Otherwise the expedition would have been a fiasco. As it was, Salonika surrendered. The army of Cantacuzenos ascended the Vardar as far as Uskub, which was reoccupied.[214] It would be too wearisome to go into all the details of the civil war between Cantacuzenos and John Palaeologos. Involved in it are the intrigues of Stephen Dushan of Serbia and Alexander of Bulgaria, and the attitude of Venice and Genoa. At first it seemed as if Cantacuzenos would be crushed. The partisans of Palaeologos besieged Matthew in the citadel of Adrianople. The Genoese of Galata, in spite of the strong Venetian fleet whose co-operation, however, with the Greeks was lukewarm,[215] compelled Cantacuzenos to cede Silivria and Heraclea, besides increasing their Galata lands.[216] In the fall of 1352 the Venetians and Bulgarians declared openly for Palaeologos.[217] In desperation Cantacuzenos fell back for the last time upon the Osmanlis. He robbed the churches of the capital to pay Orkhan for twenty thousand soldiers, and promised him a fortress in the Thracian Chersonese.[218] With this help he recaptured Adrianople, and relieved Matthew, who was still holding the citadel. The Serbians were beaten by Orkhan’s eldest son, Soleiman, near Demotika. All of Thrace and most of Macedonia returned to the allegiance of Cantacuzenos.[219] In 1353 Cantacuzenos seemed to have recovered all the lost ground, and to be at the height of his fortunes. John Palaeologos, abandoned by his partisans, was in exile at Tenedos. An attempt to win back Constantinople by intrigue failed. Cantacuzenos, now practically sole ruler, felt that it was time to establish a new imperial line. He had Matthew proclaimed co-emperor.[220] In his prosperity he forgot about Orkhan, who had put him where he was, he forgot that he had invited the Osmanlis into Europe and had shown them the fertile valleys of Macedonia and Thrace, that their fighting men had passed along the military roads of the empire under the command of himself and his son, that he had mustered Ottoman armies under the walls of Salonika, of Adrianople, of Demotika, and even of Constantinople. XII