What then is the reason of the Roman success, and was is it that defeats the purpose of those who use the phalanx?
It is because in war the time and place of action is uncertain and the phalanx has only one time and one place in which it can perform its peculiar service.
Now, if the enemy were obliged to adapt themselves to the times and places required by the phalanx when a decisive battle was impending, those who use the phalanx would in all probability, for the reasons I stated above, always get the better of their enemies;
but if it is not only possible but easy to avoid its onset why should one any longer dread an attack of a body so constituted?
Again, it is acknowledged that the phalanx requires level and clear ground with no obstacles such as ditches, clefts, clumps of trees, ridges and water courses,
all of which are sufficient to impede and break up such a formation.
Every one would also acknowledge that it is almost impossible except in very rare cases to find spaces of say twenty stades or even more in length with no such obstacles.
But even if we assume it to be possible, supposing those who are fighting against us refuse to meet us on such ground, but force round sacking the cities and devastating the territory of our allies, what is the use of such a formation?
For by remaining on the ground that suits it, not only is it incapable of helping its friends but cannot even ensure its own safety.
For the arrival of supplies will easily be prevented by the enemy, when they have undisturbed command of the open country.
But if the phalanx leaves the ground proper to it and attempts any action, it will be easily overcome by the enemy.
And again, if it is decided to engage the enemy on level ground, but instead of availing ourselves of our total force when the phalanx has its one opportunity for charging, we keep out of action even a small portion of it at the moment of the shock, it is easy to tell what will happen from what the Romans always do at present,
Walbank Commentary