Early career Demetrius served with his father,
Antigonus I Monophthalmus, during the
Second War of the Diadochi. He participated in the
Battle of Paraitakene where he commanded the cavalry on the right flank. Despite the Antigonid left flank, commanded by
Peithon, being routed, and the center, commanded by Antigonus, being dealt heavy losses at the hands of the famous
Silver Shields, Demetrius was victorious on the right, and his success there ultimately prevented the battle from being a complete loss. Demetrius was again present at the conclusive
Battle of Gabiene. Directly after the battle, while Antigonus held the betrayed
Eumenes, Demetrius was one of the few who implored his father to spare the Greek successor's life. At the age of twenty-one he was left by his father to defend
Syria against
Ptolemy the son of
Lagus. He was defeated at the
Battle of Gaza, but soon partially repaired his loss by a victory in the
Battle of Myus, against a general of Ptolemy,
Cilles. In the spring of 310, he was soundly defeated when he tried to expel
Seleucus I Nicator from
Babylon; his father was defeated in the autumn. As a result of this
Babylonian War, Antigonus lost almost two thirds of his empire: all eastern satrapies fell to Seleucus. After several campaigns against Ptolemy on the coasts of
Cilicia and
Cyprus, Demetrius sailed with a fleet of 250 ships to
Athens. He freed the city from the power of
Cassander and Ptolemy, expelled the garrison which had been stationed there under
Demetrius of Phalerum, and besieged and took
Munychia (307 BC). After these victories he was worshipped by the Athenians as a
tutelary deity under the title of
Soter (, "Saviour"). At this time Demetrius married Eurydike, an Athenian noblewoman who was reputed to be descendant from
Miltiades; she was the widow of
Ophellas, Ptolemy's governor of
Cyrene. Antigonus sent Demetrius instructions to sail to Cyprus and attack Ptolemy's positions there. Demetrius sailed from Athens in the spring of 306 BC and in accordance with his father's orders he first went to Caria where he summoned the
Rhodians in an unsuccessful attempt to support his naval campaign. In the campaign of 306 BC, he defeated Ptolemy and
Menelaus, Ptolemy's brother, in the naval
Battle of Salamis, completely destroying the naval power of
Ptolemaic Egypt. Following the victory, Antigonus assumed the title "king" and bestowed the same upon his son Demetrius. In 305 BC, he endeavoured to punish the
Rhodians for having deserted his cause; his ingenuity in devising new
siege engines in his (ultimately unsuccessful) attempt to reduce the capital gained him the title of Poliorcetes. He also sought the attention of Lamia, a Greek courtesan. He demanded 250 talents from the Athenians, which he then gave to Lamia and other courtesans to buy soap and cosmetics.
King of Macedonia possibly depicting
Lanassa and Demetrius I, ca. 50–40 BC. In 294 BC, he established himself on the throne of Macedonia by murdering
Alexander V, the son of Cassander. He faced rebellion from the
Boeotians but secured the region after
capturing Thebes in 291 BC. That year he married
Lanassa, the former wife of
Pyrrhus, but his new position as ruler of Macedonia was continually threatened by Pyrrhus, who took advantage of his occasional absence to ravage the defenceless part of his kingdom (
Plutarch,
Pyrrhus, 7 ff.); at length, the combined forces of Pyrrhus, Ptolemy and Lysimachus, assisted by the disaffected among his own subjects, obliged him to leave Macedonia in 288 BC. After
besieging Athens without success he passed into Asia and attacked some of the provinces of Lysimachus with varying success. Famine and pestilence destroyed the greater part of his army, and he solicited Seleucus' support and assistance. However, before he reached Syria hostilities broke out, and after he had gained some advantages over his son-in-law, Demetrius was totally forsaken by his troops on the field of battle and surrendered to Seleucus. His son
Antigonus offered all his possessions, and even his own person, in order to procure his father's liberty, but all proved unavailing, and Demetrius died after a confinement of three years (283 BC). His remains were given to Antigonus and honoured with a splendid funeral at
Corinth. His descendants remained in possession of the Macedonian throne until the time of
Perseus, when Macedon was conquered by the
Romans in 168 BC. == Legacy ==