But it must not be supposed that Constantine’s activity was entirely engrossed in persecuting the worshippers of images. The thirty-five years of his reign were a period of considerable military glory, and the emperor, who always headed his own armies, took the field for more than a dozen campaigns. In Asia the fall of the Ommeyad Caliphs, accompanied by savage civil wars among the Saracens (750), offered an unrivalled opportunity for extending the bounds of the empire. [Sidenote: Wars of Constantine.] Constantine pushed beyond the Anti-Taurus as far as the Euphrates; in 745 he occupied the district of Commagene, and transported all its Christian inhabitants to Thrace: in 751 he took Melitene on the Euphrates, and the great Armenian fortress of Theodosiopolis. Part of these conquests were afterwards recovered by the first Abbaside Caliph, Abdallah Al-Saffah, but the rest remained to the empire as a trophy of Constantine’s wars. Several Saracen attempts to invade Cappadocia and Cyprus were driven back with great slaughter, and in general it may be stated that Constantine effectually protected Asia Minor from the Mohammedan sword, and that the country began to grow again both in wealth and in population. Nor was his work less useful in Europe. He completely reduced to order the Slavonic tribes south of the Balkan, both in Thrace and Macedonia: they had got out of hand during the troubles of the years 605-718, and required to be subdued anew. Constantine carefully fortified the defiles of the Balkans, which communicate with the valley of the Danube, garrisoning once more the ruined castles which Justinian had built there. This advance northward brought him into hostile contact with the Bulgarians, who had long been accustomed to harry both the Slavonic and the Roman districts of Thrace and Macedon, and could not brook to be walled in by the new line of forts. Constantine waged three successful wars with the Bulgarians; the first, lasting from 755 to 762, ended with a great victory at Anchialus, after which king Baian sued for peace, and obtained it on promising to keep his subjects from raiding across the Balkans. The second war occupied the years 764-773. Constantine crossed the Balkans, wasted Bulgaria, slew the new king Toktu near the Danube, and was preparing in the next year to complete the conquest of the country, when his whole fleet and army were destroyed by a storm in the Black Sea (765). Long and indecisive bickering on the line of the Balkans followed, and peace was made in 773 on the old terms. The last Bulgarian war, provoked by an attempt of king Telerig to invade Macedonia in 774-5, was notable for a great victory at Lithosoria, but Constantine died while leading his army northward, and his successes had no permanent result. The Bulgarians were not subdued by him, but they were kept at bay, and so tamed that they were compelled to leave Thrace alone, and content themselves with defending their own Danubian plains