Just ask Hannibal Barca

From Wikipedia;
Upon the onset of the battle [ of Cannae,] the Carthaginian centre withdrew before the advance of the numerically superior Romans. While Hannibal's centre line yielded, the Romans had unknowingly driven themselves into a large arc whereupon the Carthaginian infantry and cavalry (positioned on the flanks) encircled the main body of Roman infantry. Surrounded and attacked on all sides with no means of escape, the Roman army was subsequently cut to pieces.

Dante