At the Battle of Gaugamela, October 1st, 331 BC, Alexander the Great’s army was outnumbered by that of the Persian king, Darius, who positioned himself at the center of his lines, with cavalry to either side, and chariots in front (see map above). Alexander beat him by pulling off one of history’s most successful battlefield tactical deceptions.
Alexander rode off with most of his cavalry, including his elite Companion Cavalry, towards the right of the field, accompanied by a scratch force of infantry, whom he interposed between his cavalry on that side of the field and the Persian chariots, to keep the chariots from striking the Macedonian cavalry’s exposed flank as he rode towards the right of the field. The Persian cavalry opposite Alexander shadowed him, riding parallel toward the right side of the map, to ensure he did not outflank the Persian line. That was what Alexander wanted: to remove as much of the Persian cavalry from their initial position as possible.
Alexander had a surprise for the Persian cavalry: while riding off toward the right, he had some light infantry keeping pace with him, but concealed from Persian sight by Alexander’s cavalry between the Persians and Alexander’s light infantry. The result was three parallel lines moving towards the right side of the map: the Persian cavalry, Alexander’s cavalry, whom the Persians could see, and Alexander’s light infantry, whom the Persians could not see and of whose existence they were unaware.
The Persian cavalry, shadowing Alexander as he moved to the right, eventually got ahead of him and outflanked what they assumed had been Alexander’s attempt to outflank them. Then, having gained the “advantage”, the Persian cavalry charged Alexander. That was precisely what Alexander had hoped they would do: in shadowing him and keeping pace as he rode to the right of the field, a gap had opened in the Persian line. A gap where the Persian cavalry had been at the start of the battle, and Alexander’s goal all along had been to draw the Persian cavalry out of position in order to produce that very gap (see map below).
That was when Alexander’s concealed light infantry came into play: when the Persian cavalry charged, Alexander released the hitherto concealed light infantry to engage the Persian cavalry, and left them, along with most of his cavalry, to keep the Persian cavalry busy. Then, he neatly disengaged his elite Companion Cavalry from the fray, and turning direction, rode back at their head in a wedge formation, straight for the gap in the Persian line where the Persian cavalry had been at the start of the battle.
A gap where the Persian king, Darius, happened to be. It was a surgical strike that won the day. Seeing Alexander leading a furious cavalry charge straight at him, without enough cavalry of his own in position to ward him off, Darius panicked and fled the battlefield. The Gaugamela battle scene in the movie Alexander faithfully depicted this maneuver as it was described by contemporary writers in Alexander’s day.