Bulgaria, too, refused help to the Greeks when the Turkish invasion had to be beaten off. The Turks' coming to the Balkans was thus largely due to Christian divisions. [Illustration: _Sébah & Joaillier_ SANCTA SOPHIA, CONSTANTINOPLE Built by Justinian I, consecrated 538, converted into a Mohammedan mosque 1453. It is now thought that the design of its famous architect, Anthemius of Tralles, was never completed. The minarets and most of the erections in the foreground are Turkish] Without being able at the time to capture Constantinople, the invading Turks occupied soon a large tract of the Balkan Peninsula. By 1362 they had captured Philippopolis and Eski Zagora, two important centres of Bulgaria. It was not a violence to their conscience for some of the Bulgarian men after this to join the Turkish army as mercenaries. When the sorely-beset Greeks sent the Emperor John Paleologos to appeal for help to the Bulgarians, he was seized by them and kept as a prisoner. A united Balkan Peninsula would have kept off the Turks, no doubt. But a set of small nations without any faculty of permanent cohesion, and hating and distrusting one another more thoroughly than they did the Turk, could do nothing. The Balkan nations of the time, though united they would have been really powerful, allowed themselves to be taken in detail and crushed under the heels of an invader who was alien in blood and in religion. In 1366 the Bulgarians became the vassals of the Turks, and the Serbians were defeated at Kossovo. The fall of the Greek Empire and the subjugation of Roumania followed in due course, and by the seventeenth century the Turks had penetrated to the very walls of Vienna. At one time it seemed as if all Europe would fall under the sway of Islam, for, as elsewhere than in the Balkans, there were Christian States which were treacherous to their faith. But that happily was averted. For the Balkan Peninsula, however, there were now to be centuries of oppression and religious persecution. It will be convenient once again to set forth under three national headings the chief facts regarding the Turkish conquest of the Balkans.