The first important military command was given to Demetrius when Ptolemy, king of Egypt, invaded Syria. Antigonus himself remained in Phrygia, but he sent his son, then just twenty-two years of age, as sole commander of his army. But inexperience made the young man rash, and he met with a great defeat near the town of Gaza. Eight thousand of his men were taken, five thousand were killed, and all his private property, including his tent and money, captured. Ptolemy afterwards returned everything except the prisoners, saying that he was fighting only for dominion.

Demetrius bore his defeat like a well-tried general, and immediately set to work to prepare for another battle, which soon took place with Cilles, Ptolemy's lieutenant. Cilles thought it a trifling matter to drive a young commander, already defeated, out of Syria, but he soon found that he had undervalued his antagonist, for Demetrius took him by surprise and captured him, seven thousand prisoners of war, and a large amount of treasure. He was not more delighted at the victory than he was at the opportunity it gave him of returning Ptolemy's generosity. So having obtained his father's permission, he sent back Cilles and his friends loaded with presents. This battle drove Ptolemy out of Syria.

Some time after, Antigonus and his son determined to free Greece from the slavery to which she had been reduced by Cassander and Ptolemy. This was a just and noble desire, and Demetrius set sail for Athens with a fleet of two hundred and fifty ships. He reached the Piræus, the harbor of Athens, before his approach had been made known, and as his ships were supposed to have been sent by Ptolemy, he got well into the harbor before the mistake was discovered; then the generals who had hastened to the shore were so frightened that they became helpless. Demetrius went upon the deck of his vessel, and, after motioning to the people on shore to keep silence, ordered a herald to make this proclamation: "Antigonus, my father, in a happy hour, I hope, for Athens, has sent me to give the citizens back their liberty, to turn out the garrison sent here by Cassander, and to restore to the country its ancient laws."

On hearing this the people threw down their shields and clapped their hands with delight, calling Demetrius their deliverer and benefactor. They invited him to land, but he would not do so until he had driven out Cassander's garrisons from other ports, as well as from Athens. This took considerable time, and then he made his entrance into the city, publicly announcing to the people that they were now free, and that they should receive from Antigonus, his father, a present of wheat, and a supply of timber sufficient to build a hundred galleys. So, after fifteen years, the Athenians had their laws and institutions again restored to them.

But they were so servile in their gratitude that they showed themselves unfit for liberty. They bestowed such excessive honors on Demetrius as to be positively offensive, for they gave him and his father the title of king, though they had no claim to it, and called them besides their Tutelar Deities and Deliverers. But this was not all: by a common vote they decreed that each year was to be named by a priest of the two Tutelary Divinities, whose title should appear on all public documents. The figures of Antigonus and Demetrius, they decreed, should be wrought into the holy garments with those of the other gods; they built an altar on the spot where Demetrius first landed, calling it the "Altar of the Descent of Demetrius," and created two new tribes, called the Antigonid and the Demetriad. Their council consisted of five hundred persons, fifty being chosen out of each tribe. They added a hundred more to represent the new tribes, and further agreed that any ambassadors sent from Athens to Antigonus or Demetrius should have the same title as those sent to Delphi or Olympia to perform the national sacrifices, and that whenever Demetrius should visit their city he should be treated as though he were a god, the citizen who excelled the rest in his feast being promised money from the public purse for sacrifice. They also instituted a feast of Demetrius, and named a month in his honor.

Indeed, with all this disgusting flattery, Demetrius would have had his head completely turned if his father had not summoned him to undertake the reduction of Cyprus. He sailed for that island as soon as he received the order, fought a battle with Menelaus, the brother of Ptolemy, and defeated him. Then Ptolemy himself came with large forces and a numerous fleet, but Demetrius was prepared for him, and a great fight took place in the harbor of Salamis, the ancient capital of Cyprus, which ended in a complete rout of the Egyptian army. Ptolemy escaped with eight ships, the rest, with all their men, being taken or destroyed in the battle. Demetrius seized the arms, treasures, and military machines, and took them to his camp; but what added more to his glory than any victory could have done was his humane conduct. After he had given honorable funerals to the dead, he bestowed on the prisoners their liberty, and to prove to the Athenians that they were not forgotten he sent them full sets of arms for twelve hundred men.

Aristodemus was despatched with the news of victory to Antigonus, who waited in great anxiety to hear the result of the battle. This man was the boldest of all the court flatterers, and on this occasion he made it a study how to produce the best effect and to bring out the full importance of his welcome message. So when he crossed from Cyprus he bade the crew remain on board the ship, and, getting into a little boat, landed quite alone. When the anxious father heard that a messenger was coming from Cyprus he sent one person after another to get the news and hasten to him with it. But not a word could they draw from Aristodemus, who walked gravely and quietly towards the palace, determined to tell his story in his own way to Antigonus. He was so long about it, and looked so very grave, that it was generally believed by those who met him that his news was bad, and so thought the impatient Antigonus, who, no longer able to restrain his anxiety, ran out, followed by a crowd of people, and met the messenger at the gate. "Hail, King Antigonus!" exclaimed Aristodemus, holding out his hands and making a profound bow. "We have defeated Ptolemy by sea, and have taken Cyprus and sixteen thousand eight hundred prisoners."

"Welcome, Aristodemus," replied Antigonus; "but, as you chose to torture us so long for your good news, you may wait awhile for the reward of it."

Then all the people saluted Antigonus as king, and for the first time gave him the title which the Athenians had bestowed on him. A crown was procured and placed upon his head, and shortly after he sent one to his son, with a letter addressed to "King Demetrius."

So elated was Antigonus with his success that he set out in person to invade Egypt, but he met with many difficulties; and as he was nearly eighty years old and very fat, he decided that it would be better to leave conquest to his son, and so returned home without having accomplished anything.

Now the Rhodians persisted in their friendship for Ptolemy; so Demetrius was ordered to fight them. He laid siege to Rhodes, and used on that occasion the most powerful of the engines he had invented. These "city-takers," as they were called, were the wonder and admiration of the world. The one used before Rhodes was the largest; it was a hundred and fifty feet high, supported on eight enormous wheels, and required three thousand four hundred men to move it. It was nine stories high, square at the base, and growing smaller as it rose. Each story was filled with soldiers, and there were windows from which all sorts of weapons were discharged against the enemy's walls. In spite of this formidable engine, the Rhodians made a brave defence, and held out for a whole year.

Demetrius had known for a long time that he was making little progress, so he rejoiced when a reasonable excuse for raising the siege presented itself. This came in the shape of an appeal for aid from the Athenians, whose city Cassander was besieging. Then a treaty was made with the Rhodians, who bound themselves to aid Antigonus and Demetrius against all enemies except Ptolemy.

Demetrius went to Athens with a fleet of three hundred ships and a large army, and not only drove Cassander out of Athens, but restored liberty by the terror of his arms to the whole of Greece. Then the Athenians thought no place good enough for him to occupy but the Parthenon itself, where he was supposed to be the guest of the goddess Minerva.

But he did not enjoy this new honor long, for several kings formed a league on purpose to attack Antigonus, and his son was called home. The old king headed the army himself; and although he said, "This flock of birds will soon be scattered by one stone and a single shout," he had his misgivings when he saw the tremendous army the kings had brought against him. The great battle was fought at Ipsus, and Antigonus fell pierced by a score of darts.

Demetrius managed, after several narrow escapes, to set sail for Athens, where he felt sure of a hearty welcome; he was therefore astonished when he received a message from the changeable and ungrateful inhabitants that they had resolved to receive no king within their walls. Demetrius was justly angry, but he was not in condition to avenge the insult; he merely sent a gentle remonstrance and a demand for his galleys, which were sent to him.

Not long after, fortune smiled on Demetrius again, for Seleucus, one of the most powerful of all Alexander's generals, became jealous of the vast territory owned by Lysimachus, and tried to strengthen himself by seeking a friendship with his former enemy, Demetrius; so he wrote to him, asking the hand of his daughter in marriage. This pleased Demetrius so much that he sailed for Syria at once, with his daughter and his whole fleet.

When Seleucus and Demetrius met, each gave the other a grand banquet, and after several unceremonious meetings they parted excellent friends. Seleucus took his wife with him, and they travelled in great state. He also brought about a reconciliation between Demetrius and the king of Egypt, whose daughter, Ptolemais, afterwards married Demetrius.

The ingratitude of the Athenians had been very galling to Demetrius, so when news came to him of disturbance in the city, he resolved to go and take possession of it by a sudden attack. But while passing along the coast of Attica he was overtaken by a violent storm, and lost most of his ships and men. It did not take him long to raise more troops, and with these he marched into the Peloponnesus and laid siege to the city of Messena. Thence he made an incursion into Attica and cut off supplies, so that the people were almost starved to death.

So great was the distress that any sort of food became acceptable. An instance is given of a father and son who actually came to blows over a dead mouse that fell from the ceiling, for they were so hungry as to have lost sight of every other consideration. the philosopher, saved his own life and the lives of his scholars by daily dividing a small quantity of beans.

Such being the condition of the Athenians, they were forced at last to open their gates to Demetrius, and sent ambassadors to know what sort of a treaty he would make with them. He entered the city, and issued a proclamation that all the inhabitants should assemble at the theatre. When they had done so, he ranged his soldiers in a line at the back of the stage, then coming forward like an actor, he gently upbraided the Athenians for their ill treatment of himself, but added that he forgave them, and would present them with a hundred thousand bushels of wheat, in token of reconciliation, to relieve their wants. He also appointed such magistrates as he knew would be most agreeable to them. Having thus settled matters in Athens, he next turned his attention to Macedonia, where, the king having died, his two sons quarrelled about the succession. Alexander, one of the sons, wrote to Demetrius asking his assistance, which was freely given. But after he had been in Macedonia a short time, Demetrius heard of a plot formed by Alexander to kill him, so in order to turn the tables on him he invited the young prince to sup with him. When the meal was nearly over, Demetrius rose and went out; the prince followed. "Kill him that follows me," said Demetrius to the guard. His order was forthwith executed. A friend who had accompanied Alexander said, "You have been just one day too quick for us, Demetrius."

The other prince had murdered his mother, and had thus made himself hateful to the people, who, as soon as they found no violence offered to themselves, proclaimed Demetrius king of Macedon.

Even then he could not rest, for his ambitious spirit demanded more power; so he marched with his troops against Pyrrhus, drove him out of Thessaly, and then besieged and took Thebes. But Pyrrhus was a brave man, and his conduct in battle won for him the greatest glory among the Macedonians, who kept constantly comparing his valor with that of their beloved Alexander the Great.

Meanwhile, Demetrius was exciting their disgust because he was so theatrical in his manners, so haughty, and so fond of display. His robes were of the richest purple material, embroidered and edged with gold; his crown was the most gorgeous that had ever been worn by any Macedonian king, and even his shoes were gayly and elaborately ornamented. He lived in most luxurious style, and was so reserved that his subjects dared not approach him, or if they did he treated them with overbearing pride. He kept the Athenian ambassadors waiting two whole years before he would give them an audience, and when the Lacedæmonians sent one person to confer with him, he asked angrily whether they had really dared to send a single envoy. "Yes," they said, boldly, "one envoy to one king."

One day, when he was riding out and seemed to be in a more amiable mood than usual, several of his subjects approached him with petitions. They were so pleased to see him take the papers and gather them into his robe that they followed him; but when he reached the river he shook them all into the water, without having so much as opened them. Such acts were often repeated, until the Macedonians felt that Demetrius no longer governed them, but insulted them.

So, when he collected a great army to invade Asia, Pyrrhus and Lysimachus took that opportunity to attack Macedonia, and they were received with such favor that they divided the country between them. Then the soldiers of Demetrius deserted from his camp, and in order to save himself he put on a disguise and stole away.

For a while he was dejected, but his active spirit soon revived, and he collected an army, which he led into Asia Minor. There he had great success at first, but ill fortune overtook him, and after much suffering he was forced to seek the protection of Seleucus, his son-in-law. Seleucus knew it was dangerous to have within his territory a man who was so fond of bold enterprises; however, he granted him permission to stay two months. But the courtiers were displeased at this favor, and before the allotted period had expired they persuaded their king to send him to a strong fortress on the Syrian coast. There the prisoner was well attended and well fed, he had plenty of space for walking and riding, and a park with game for hunting, and those of his friends and companions in exile who desired to visit him had permission to do so.

At first restraint seemed irksome to Demetrius, but he sank into idle habits before very long, and passed most of his time in gambling and drinking. Such a life brought on a disease of which, in the course of three years, Demetrius died, at the age of fifty-four.

His remains were sent in a golden urn to Greece, where they were received by his son, Antigonus, who conveyed them to the city of Demetrius. As the galley passed along the coast, wherever it touched land the people sent chaplets to adorn the urn. When the vessel entered the harbor of Corinth, a famous musician played a solemn tune on the flute, to which the rowers kept time, and a troop of young men in arms stood in a line when the urn, covered with purple and surmounted by a royal diadem, was carried ashore. In tears and mourning Antigonus bore it to its final resting-place.