Quote Originally Posted by Laconic
What happened to the phalanx? The Romans did. The phalanx was impenetrable to infantry or cavalry attacks from the front, but its flanks are quite a different matter. Later armies would learn to exploit this. Another tactic used against them was missile fire, specifically javelins. The Romans made use of a lighter troop type (the legions) that could outmaneuver the densely-packed phalanx.

The Romans dominate due to their advanced politocoeconomical structure, the HUGE vacuum that Alexander's death left, the complete disindegration of the shock Hetairoi cavalry by the successors and the fact that couched lance tactic and stirrups havent been invented...yet.
Once these came into play the almighty Roman legion crumbled under the charge of cavalry men because you just cant stop a charge with a short sword....
The Roman legionary died and never revived while the Pike phalanx revived to kill another gloryfied and hyped up myth: The knight....