This comes out most often as a note of warning; like the _motif_ of Ortrud in the opera of "Lohengrin," it mingles ominously in every chorus of Hellenic enterprise or paean of Hellenic victory, and finally swells into a national dirge at the Turkish conquest of the peninsula.

It comes out in the legendary history of the Argonautic Expedition and the Trojan War; in the arrival of Phoenician Cadmus and Phrygian Pelops in Grecian lands; in the appearance of Tyrian ships on the coast of the Peloponnesus, where they gather the purple-yielding murex and kidnap Greek women.

It appears more conspicuously in the Asiatic sources of Greek culture; more dramatically in the Persian Wars, in the retreat of Xenophon's Ten Thousand, in Alexander's conquest of Asia, and Hellenic domination of Asiatic trade through Syria to the Mediterranean.

Again in the thirteenth century the lure of the Levantine trade led Venice and Genoa to appropriate certain islands and promontories of Greece as commercial bases nearer to Asia.

In 1396 begins the absorption of Greece into the Asiatic empire of the Turks, the long dark eclipse of sunny Hellas, till it issues from the shadow in 1832 with the achievement of Greek independence.
[Sidenote: Persistent effect of natural barriers.] If the factor is not one of geographical location, but a natural barrier, such as a mountain system or a desert, its effect is just as persistent.