The Sarakatsani traditionally have spent the summer months in the mountains and returned to the lower plains in the winter. The migration would start on the eve of Saint George's day in April and the return migration would begin on Saint Demetrius' day, on 26 October. However, according to a theory, the Sarakatsani were not always nomads, but only turned to harsh nomadic mountain life to escape Ottoman rule. The Sarakatsani were found in several mountainous regions of continental Greece, with some groups of northern Greece moving to neighbouring countries in the summer, since border crossings between Greece, Albania, Bulgaria and the former Yugoslavia were relatively unobstructed until the middle of the 20th century. After 1947, with the beginning of the Cold War, borders between these countries were sealed; and some Sarakatsani groups were trapped in other countries and not able to return to Greece.