What was the advantage of roman legion?

Answer 1

Phalanxes facing the legion were more vulnerable to the more flexible Roman "checkboard" deployment. The checkboard deployment allowed the Romans more room to maneuver and let them apply steady combat pressure on the enemy, when one line was exhausted they would easily withdraw and let the next line carry on the fight till they were refreshed. The phalanx on the other hand had very little space to maneuver and each line fought its own lonely battle and ultimately perished under continuous Roman attacks.

In the Battle of Cynoscephalae, The Roman legionaires were trained to actually duck under the spears of the oncoming phalanx, crawl up to the Macedonian soldiers, thrust up with their pilum, and voila, Greece became a Roman province.

ANSWER

The question is not as precise as it should be as one cannot realy compare a phalanx to a legion. They were quite different size combat units and while the phalanx consisted only in a body of soldiers of a few hundred at most and only weilding long spears, the legion was constructed somewhat similar to a modern army group, and numbered upwards of 5000.

One roman legion included a main corp of infantrymen, a corp of auxilliares that manned the heavy weapons and siege machines, spearmen to counter cavalery charges, skirmishers and archers plus a unit of heavy cavalery and one of scout cavalery and "legati".

The phalanx was, as I said just a body of infantrymen armed with 6-7 m long spears and small shields that was meant to slowly crush through another rigid unit of infantery and was thus utterly useless and completely vulnerable against all of the other units forming a Roman legion. Unsupported by cavalery and the hoplite heavy infantery the phalanx cannot be pinned against a legion. At least successfully, that is.

Answer 2

The Roman legions originally used the phalanx formation. This was replaced by the manipular formation during the Samnite Wars against the Samnites of southern Italy. The Roman adopted the manipular formation of the Samnites because it was more flexible. The maniples were then replaced by the cohort formation. This remained more flexible than the phalanx.

Answer 3

Greek phalanxes were less flexible than Roman legions