The art of war made a great advance under the Greeks, although we do not notice any striking superiority of arms over the Eastern armies led by Sesostris or Cyrus. The Greeks were among the most warlike of all the races of men; they had a genius for war. The Grecian States were engaged in perpetual strifes with one another, and constant contention developed military strength; and yet the Greeks, until the time of Philip, had no standing armies. They relied for offence and defence on the volunteer militia, which was animated by intense patriotic ideas. All armies in the nature of things are more or less machines, moved by one commanding will; but the Greek armies owed much of their success to the individual bravery of their troops, who were citizens of States under constitutional forms of government. The most remarkable improvement in the art of war was made by the Spartans, who, in addition to their strict military discipline, introduced the _phalanx_,--files of picked soldiers, eight deep, heavily armed with spear, sword, and shield, placed in ranks of eight, at intervals of about six feet apart. This phalanx of eight files and eight ranks,--sixty-four men,--closely locked when the soldiers received or advanced to attack, proved nearly impregnable and irresistible. It combined solidity and the power of resistance with mobility. The picked men were placed in the front and rear; for in skilful evolutions the front often became the rear, and the rear became the front. Armed with spears projecting beyond the front, and with their shields locked together, the phalanx advanced to meet the enemy with regular step, and to the cadence of music; if beaten, it retired in perfect order. After battle, each soldier was obliged to produce his shield as a proof that he had fought or retired as a soldier should. The Athenian phalanx was less solid than that of Sparta,--Miltiades having decreased the depth to four ranks, in order to lengthen his front,--but was more efficient in a charge against the enemy. The Spartan phalanx was stronger in defence, the Athenian more agile in attack. The attack was nearly irresistible, as the soldiers advanced with accelerated motion, corresponding to the double-quick time of modern warfare. This was first introduced by Miltiades at Marathon.