What were the advantages of the Roman military system over the Greek phalanx?

Its advantage was that such a system was flexible and could change as the situation changed. The Greek phalanx was very clumsy. She could show herself well only on flat territory, and on rough terrain, her combat effectiveness fell. In addition, the flanks of the Greek phalanx were very vulnerable, since the battle formation did not provide for the repulsion of attacks from the flanks. The Roman legionaries were in a better position in this regard.