The Hellenic Diaspora (Dispersion) is the collective term for the process which began with the accelerated destruction of the captured Greek territories by the Roman Empire. Some Greeks interpret diaspora as exile, others as a positive aspect of Hellenism's ethnic and spiritual destiny, who remained loyal to their faith, ethnicity and homeland. The beheading of Archimedes was the beginning of the brain drain of Greeks to the Middle East, Asia and Northern Africa. The existence of these diaspora communities was also an important factor in the spread of Christianity. By the early Middle Ages Europe was the centre of Hellenic scholarship, but from the time of the Crusaders, anti-orthodoxy and the persecution of Hellenes begun. Eastern Europe welcomed Greek victims of persecution and by the 17th century Eastern Europe had become the diaspora's centre, until the massacres of the 1821 and 1915 by the Ottomans, thus many Greeks migrated to Germany, Britain and the USA.