Demetrius   

justice that was part of Demetrius's natural character.
But as in the elements of the world, Empedocles tells us, out of
liking and dislike, there springs up contention and warfare, and all
the more, the closer the contact, or the nearer the approach of the
objects, even so the perpetual hostilities among the successors of
Alexander were aggravated and inflamed, in particular cases, by
juxtaposition of interests and of territories; as, for example, in the
case of Antigonus and Ptolemy. News came to Antigonus that Ptolemy had
crossed from Cyprus and invaded Syria, and was ravaging the country
and reducing the cities. Remaining, therefore, himself in Phrygia,
he sent Demetrius, now twenty-two years old, to make his first essay
as sole commander in an important charge. He, whose youthful heat
outran his experience, advancing against an adversary trained in
Alexander's school, and practised in many encounters, incurred a great
defeat near the town of Gaza, in which eight thousand of his men
were taken and five thousand killed. His own tent, also his money, and
all his private effects and furniture, were captured. These,
however, Ptolemy sent back, together with his friends, accompanying
them with the humane and courteous message, that they were not
fighting for anything else but honour and dominion. Demetrius accepted
the gift praying only to the gods not to leave him long in Ptolemy's
debt, but to let him have an early chance of doing the like to him. He
took his disaster, also, with the temper, not of a boy defeated in his
attempt, but of an old and long-tried general familiar with reverse of
fortune; he busied himself in collecting his men, replenishing his
magazines, watching the allegiance of the cities, and drilling his new
recruits.
Antigonus received the news of the battle with the remark that
Ptolemy had beaten boys and would now have to fight with men. But
not to humble the spirit of his son, he acceded to his request, and
left him to command on the next occasion.
Not long after, Cilles, Ptolemy's lieutenant, with a powerful
army, took the field, and looking upon Demetrius as already defeated
by the previous battle, he had in his imagination driven him out of
Syria before he saw him. But he quickly found himself deceived; for
Demetrius came so unexpectedly upon him that he surprised both the
general and his army, making him and seven thousand of the soldiers
prisoners of war, and possessing himself of a large amount of
treasure. But his joy in the victory was not so much for the prizes he
should keep, as for those he could restore; and his thankfulness was
less for the wealth and glory than for the means it gave him of
requiting his enemy's former generosity. He did not, however, take
it into his own hands, but wrote to his father. And on receiving leave
to do as he liked, he sent back to Ptolemy Cilles and his friends,
loaded with presents. This defeat drove Ptolemy out of Syria, and
brought Antigonus from Calaenae to enjoy the victory and the sight
of the son who had gained it.
Soon after, Demetrius was sent to bring the Nabathaean Arabs into
obedience. And here he got into a district without water, and incurred
considerable danger, but by his resolute and composed demeanour he
overawed the barbarians, and returned after receiving from them a
large amount of booty and seven hundred camels. Not long after,
Seleucus, whom Antigonus had formerly chased out of Babylon, but who
had afterwards recovered his dominion by his own efforts and
maintained himself in it, went with large forces on an expedition to
reduce the tribes on the confines of India and the provinces near
Mount Caucasus. And Demetrius, conjecturing that he had left
Mesopotamia but slenderly guarded in his absence, suddenly passed
the Euphrates with his army and made his way into Babylonia
unexpectedly; when he succeeded in capturing one of the two
citadels, out of which he expelled the garrison of Seleucus, and
placed in it seven thousand men of his own. And after allowing his
soldiers to enrich themselves with all the spoil they could carry with
them out of the country, he retired to the sea, leaving Seleucus