Once on the threshold of India, the Persians saw open before them a brilliant and lucrative career: the circumstances which prevented them from following up this preliminary success are unknown--perhaps the first developments of nascent Buddhism deterred them--but certain it is that they arrested their steps when they had touched merely the outskirts of the basin of the Indus, and retreated at once towards the west. The conquest of Lydia, and subsequently of the Greek cities and islands along the coast of the AEgean, had doubtless enriched the empire by the acquisition of active subject populations, whose extraordinary aptitude in the arts of peace as well as of war might offer incalculable resources to a sovereign who should know how to render them tractable and rule them wisely. Not only did they possess the elements of a navy as enterprising and efficacious as that of the Phoenicians, but the perfection of their equipment and their discipline on land rendered them always superior to any Asiatic army, in whatever circumstances, unless they were crushed by overwhelming numbers. Inquisitive, bold, and restless, greedy of gain, and inured to the fatigues and dangers of travel, the Greeks were to be encountered everywhere--in Asia Minor, Egypt, Syria, Babylon, and even Persia itself; and it was a Greek, we must remember, whom the great king commissioned to navigate the course of the Indus and the waters of the Indian Ocean. At the same time, the very ardour of their temperament, and their consequent pride, their impatience of all regular control, their habitual proneness to civic strife, and to sanguinary quarrels with the inhabitants of the neighbouring cities, rendered them the most dangerous subjects imaginable to govern, and their loyalty very uncertain. Moreover, their admission as vassals of the Persian empire had not altered their relations with European Greece, and commercial transactions between the opposite shores of the AEgean, inter-marriages, the travels of voyagers, movements of mercenaries, and political combinations, went on as freely and frequently under the satraps of Sardes as under the Mermnadas. It was to Corinth, Sparta, and Athens that the families banished by Cyrus after his conquest fled for refuge, and every time a change of party raised a new tyrant to power in one of the AEolian, Ionian, or Doric communities, the adherents of the deposed ruler rushed in similar manner to seek shelter among their friends across the sea, sure to repay their hospitality should occasion ever require it. Plots and counterplots were formed between the two shores, without any one paying much heed to the imperial authority of Persia, and the constant support which the subject Greeks found among their free brethren was bound before long to rouse the anger of the court at Susa. When Polycrates, foreseeing the fall of Amasis, placed himself under the suzerainty of Cambyses, the Corinthians