found themselves in serious difficulties with certain other Indo-European tribes which centuries before had moved into Europe and had taken possession of the Greek peninsula and the islands of the Ægean Sea.
These difficulties led to the three famous wars between Greece and Persia during which King Darius and King Xerxes of Persia invaded the northern part of the peninsula. They ravaged the lands of the Greeks and tried very hard to get a foothold upon the European continent.
But in this they did not succeed. The navy of Athens proved unconquerable. By cutting off the lines of supplies of the Persian armies, the Greek sailors invariably forced the Asiatic rulers to return to their base.
It was the first encounter between Asia, the ancient teacher, and Europe, the young and eager pupil. A great many of the other chapters of this book will tell you how the struggle between east and west has continued until this very day.