‘Beginnings’, wrote Teilhard de Chardin, ‘have an irritating but essential fragility.’ Only rarely can we put our finger on that precise moment and place which marks a fundamental change, whether material or spiritual. The very nature of human tradition is unfavourable to such precision. Long after the event those who look back may attempt to recover and put on record the point which separates the old from the new. But their record is bound to be a gross approximation. In tracing in the following pages such a momentous new departure among the various Slav peoples we shall be obliged to admit again and again that the true beginning is beyond our ken.

No sooner did the recurrent disasters which overtook the Roman Empire at the hands of migrating Germanic peoples seem to be coming to an end than it was realised that other peoples were ready and waiting to follow in their wake. The Slavs, from their homelands north of the Carpathian chain, had been expanding not only eastwards and westwards across the North European plain but also southwards, following the lowlands of the Black Sea coast and filtering through the mountain chain into the Central European basin. The Danube was still accounted the frontier of the civilised world. In the fifth century A.D. the main power beyond that frontier had been the Huns. Attila held sway over many Germanic tribes in the Danube basin and no doubt over some Slavs also, but the latter did not yet stand out prominently.