for Darius to pass. This defile was called the
Caspian Gates,[G] the name referring to rocks on each side. The
marching of an army through a narrow and dangerous defile like this
always causes detention and delay, and Alexander hastened forward in
hopes to overtake Darius before he should reach it. He advanced with
such speed that only the strongest and most robust of his army could
keep up. Thousands, worn out with exertion and toil, were left behind,
and many of the horses sank down by the road side, exhausted with heat
and fatigue, to die. Alexander pressed desperately on with all who
were able to follow.

[Footnote G: _Pylae Caspiae_ on the map, which means the Caspian Gates.]

It was all in vain, however; it was too late when he arrived at the
pass. Darius had gone through with all his army. Alexander stopped to
rest his men, and to allow time for those behind to come up. He then
went on for a couple of days, when he encamped, in order to send out
foraging parties--that is to say, small detachments, dispatched to
explore the surrounding country in search of grain and other food for
the horses. Food for the horses of an army being too bulky to be
transported far, has to be collected day by day from the neighborhood
of the line of march.

While halting for these foraging parties to return, a Persian nobleman
came into the camp, and informed Alexander that Darius and the forces
accompanying him were encamped about two days' march in advance, but
that Bessus was in command--the conspiracy having been successful, and
Darius having been deposed and made a prisoner. The Greeks, who had
adhered to their fidelity, finding that all the army were combined
against them, and that they were not strong enough to resist, had
abandoned the Persian camp, and had retired to the mountains, where
they were awaiting the result.

Alexander determined to set forward immediately in pursuit of Bessus
and his prisoner. He did not wait for the return of the foraging
parties. He selected the ablest and most active, both of foot soldiers
and horsemen, ordered them to take two days' provisions, and then set
forth with them that very evening. The party pressed on all that
night, and the next day till noon. They halted till evening, and then
set forth again. Very early the next morning they arrived at the
encampment which the Persian nobleman had described. They found the
remains of the camp-fires, and all the marks usually left upon a spot
w