The Probert Encyclopaedia of Warfare

PHALANX

Phalanx was the name applied to the ordinary formation adopted by Greek heavy infantry. They were drawn up in close array, shoulder to shoulder, in a line eight deep, as a rule, though the Thebans used a formation twenty- five or even fifty deep. The Macedonian phalanx was an improvement on the Greek formation, in that the men stood in a rather more open order, sixteen deep, armed with spears 640 centimetres long. In 324 BC Alexander made only the three front and the rear ranks spearmen; the intermediate ranks were composed of archers and javelin men.
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