At the time of the reconciliation with the Orthodox Church, Uglesa had completed a plan of united action with his two brothers to oppose the Ottoman invasion of Macedonia.[332] Uglesa had been informed that a great army was gathered in Adrianople, which awaited the return of Murad from Bulgaria to commence its march. Four weeks after the negotiations with the Byzantines had been successfully concluded, in the early summer of 1371, the Serbian army reached the Maritza at Cernomen,[333] between Adrianople and Svilen.[334] This battle has been confused with the earlier battle of 1363, and it is impossible to separate the accounts of the two actions.[335] The Osmanlis were again victorious. Uglesa and Goiko were drowned in the Maritza. Vukasin escaped from the field of battle only to be killed by his servant for the gold chain he wore around his neck.[336] The battle of Cernomen lost Macedonia to the Serbians. The three princes were killed. Most of the Serbian adventurers who had been the companions of Stephen Dushan, and who had profited by his Macedonian conquests, disappeared. The Osmanlis had no opposition in penetrating to the valley of the Vardar. The monk Isaias of Serres has left a graphic contemporary picture of the Ottoman invasion of Macedonia. ‘Like the birds of Heaven, the Ishmaelites spread themselves over the land, and never ceased murdering the inhabitants or carrying them off into slavery. The country was empty of men, of cattle, and of the fruits of the fields. There was no prince or leader: there was no redeemer or saviour among the people. All faded away before the fear of the Ishmaelites, and even the brave hearts of heroic men were transformed into weak hearts of women. Rightly were the dead envied by the living.’[337] The invasion of Macedonia in 1371-2 was as rapid and decisive a campaign as the invasion of Thrace had been ten years before. Kavalla, Drama and Serres were occupied by Khaïreddin and Evrenos.[338] Drama and Serres were colonized, their churches converted into mosques, and they soon became the residence of the owners of the timarets granted in eastern Macedonia. These two cities have always been the strongholds of the Mohammedan element in Macedonia, and the residence of the great Moslem landowners. The cities and villages in the valleys of the Mesta and the Struma acknowledged Murad as sovereign, and submitted without resistance to Ottoman laws and Ottoman taxation.[339] Where-ever it was safe to do so, Murad seized the lands, and appointed Ottoman governors. In districts where pacification would have proved a difficult task, he allowed Serbian chiefs to rule as his vassals.