Place-names are a good index of the extent and strength of the tide of Slav immigration. All along the coast, from the mouth of the Danube to the head of the Adriatic, the Greek and Roman names have been retained though places have often been given alternative names by the Slavonic settlers. Thrace, especially the south-eastern part, and Albania have the fewest Slavonic place-names. In Macedonia and Lower Moesia (Bulgaria) very few classical names have survived, while in Upper Moesia (Serbia) and the interior of Dalmatia (Bosnia, Hercegovina, and Montenegro) they have entirely disappeared. The Slavs themselves, though their tribal names were known, were until the ninth century usually called collectively S(k)lavini ([Greek: Sklabaenoi]) by the Greeks, and all the inland parts of the peninsula were for long termed by them ‘the S(k)lavonias’ ([Greek: Sklabiniai]). During the seventh century, dating from the defeat of the Slavs and Avars before the walls of Constantinople in 626 and the final triumph of the emperor over the Persians in 628, the influence and power of the Greeks began to reassert itself throughout the peninsula as far north as the Danube; this process was coincident with the decline of the might of the Avars. It was the custom of the astute Byzantine diplomacy to look on and speak of lands which had been occupied by the various barbarian invaders as grants made to them through the generosity of the emperor; by this means, by dint also of lavishing titles and substantial incomes to the invaders’ chiefs, by making the most of their mutual jealousies, and also by enlisting regiments of Slavonic mercenaries in the imperial armies, the supremacy of Constantinople was regained far more effectively than it could have been by the continual and exhausting use of force. BULGARIA 4 _The Arrival of the Bulgars in the Balkan Peninsula,_ 600–700