The celebrated Macedonian phalanx formed the main strength of his infantry. This force had been raised and organized by his father Philip, who on his accession to the Macedonian throne needed a numerous and quickly-formed army, and who, by lengthening the spear of the ordinary Greek phalanx, and increasing the depth of the files, brought the tactic of armed masses to the greatest efficiency of which it was capable with such materials as he possessed. [See Niebuhr's Hist. of Rome, iii. 488.] He formed his men sixteen deep, and placed in their grasp the SARISSA, as the Macedonian pike was called, which was four-and-twenty feet in length, and when couched for action, reached eighteen feet in front of the soldier: so that, as a space of about two feet was allowed between the ranks, the spears of the five files behind him projected in advance of each front-rank man. The phalangite soldier was fully equipped in the defensive armour of the regular Greek infantry. And thus the phalanx presented a ponderous and bristling mass, which as long as its order was kept compact, was sure to bear down all opposition. The defects of such an organization are obvious, and were proved in after years, when the Macedonians were opposed to the Roman legions. But it is clear that, under Alexander, the phalanx was not the cumbrous unwieldy body which it was at Cynoscephalae and Pydna. His men were veterans; and he could obtain from them an accuracy of movement and steadiness of evolution, such as probably the recruits of his father would only have floundered in attempting, and such as certainly were impracticable in the phalanx when handled by his successors: especially as under them it ceased to be a standing force, and became only a militia. [See Niebuhr.] Under Alexander the phalanx consisted of an aggregate of eighteen thousand men, who were divided into six brigades of three thousand each. These were again subdivided into regiments and companies; and the men were carefully trained to wheel, to face about, to take more ground, or to close up, as the emergencies of the battle required. Alexander also arrayed in the intervals of the regiments of his phalangites, troops armed in a different manner, which could prevent their line from being pierced, and their companies taken in flank, when the nature of the ground prevented a close formation; and which could be withdrawn, when a favourable opportunity arrived for closing up the phalanx or any of its brigades for a charge, or when it was necessary to prepare to receive cavalry.