Achaeus was a general and later a separatist ruler of part of the Greek

Ancient Greece

Ancient Greece is a civilization belonging to a period of Greek history that lasted from the Archaic period of the 8th to 6th centuries BC to the end of antiquity. Immediately following this period was the beginning of the Early Middle Ages and the Byzantine era. Included in Ancient Greece is the...

 Seleucid kingdom

Seleucid Empire

The Seleucid Empire was a Greek-Macedonian state that was created out of the eastern conquests of Alexander the Great. At the height of its power, it included central Anatolia, the Levant, Mesopotamia, Persia, today's Turkmenistan, Pamir and parts of Pakistan.The Seleucid Empire was a major centre...

. He was the son of Andromachus

Andromachus

Andromachus was an Anatolian nobleman of Greek Macedonian and Persian descent. Andromachus’ father was a wealthy nobleman who owned estates in Anatolia and his family had power in Anatolia with strong royal connections. Andromachus was the second son of Achaeus by an unnamed Greek mother and a...

, whose sister Laodice II

Laodice II

Laodice , wife of her cousin Seleucus II Callinicus, was, according to the express statement of Polybius, she was the daughter of Andromachus and sister of Seleucid General Achaeus. Laodice II bore Seleucus II five children, among them were: Antiochis, Seleucus III Ceraunus and Antiochus III the...

, married Seleucus Callinicus

Seleucus II Callinicus

Seleucus II Callinicus or Pogon , was a ruler of the Hellenistic Seleucid Empire, who reigned from 246 to 225 BC...

, the father of Antiochus III the Great

Antiochus III the Great

Antiochus III the Great Seleucid Greek king who became the 6th ruler of the Seleucid Empire as a youth of about eighteen in 223 BC. Antiochus was an ambitious ruler who ruled over Greater Syria and western Asia towards the end of the 3rd century BC...

. Achaeus himself married Laodice of Pontus

Laodice of Pontus

Laodice , was a Princess of Pontus and was one of the daughters of Mithridates II of Pontus and Laodice. She sister was Laodice III the first wife of Antiochus III the Great and her brother was Mithridates III of Pontus. She married her distant maternal cousin the Seleucid general Achaeus...

, one of the daughters to Laodice

Laodice (wife of Mithridates II of Pontus)

Laodice was a Greek Princess of the Seleucid Empire. Laodice was of Greek Macedonian and Persian descent. She was one of the daughters and youngest child born to the Seleucid Monarchs Antiochus II Theos and Laodice I. Among her siblings were her brothers Seleucus II Callinicus and Antiochus Hierax...

 and Mithridates II of Pontus

Mithridates II of Pontus

Mithridates II , third king of Pontus and son of Ariobarzanes, whom he succeeded on the throne. He was a minor when his father died, but the period of his accession cannot be determined...

. He accompanied Seleucus Ceraunus

Seleucus III Ceraunus

Seleucus III Soter, called Seleucus Ceraunus , was a ruler of the Hellenistic Seleucid Kingdom, the eldest son of Seleucus II Callinicus and Laodice II. His birth name was Alexander and was named after his great uncle the Seleucid official Alexander...

, the son of Callinicus, in his expedition across mount Taurus

Taurus Mountains

Taurus Mountains are a mountain complex in southern Turkey, dividing the Mediterranean coastal region of southern Turkey from the central Anatolian Plateau. The system extends along a curve from Lake Eğirdir in the west to the upper reaches of the Euphrates and Tigris rivers in the east...

 against Attalus I

Attalus I

Attalus I , surnamed Soter ruled Pergamon, an Ionian Greek polis , first as dynast, later as king, from 241 BC to 197 BC. He was the second cousin and the adoptive son of Eumenes I, whom he succeeded, and was the first of the Attalid dynasty to assume the title of king in 238 BC...

, and after the assassination of Seleucus revenged his death; and though he might easily have assumed the royal power, he remained faithful to the family of Seleucus.

In 223 BC Antiochus III, the successor of Seleucus, appointed him to the command of all Asia Minor

Asia Minor

Asia Minor is a geographical location at the westernmost protrusion of Asia, also called Anatolia, and corresponds to the western two thirds of the Asian part of Turkey...

 on the western side of Mount Taurus

Taurus Mountains

Taurus Mountains are a mountain complex in southern Turkey, dividing the Mediterranean coastal region of southern Turkey from the central Anatolian Plateau. The system extends along a curve from Lake Eğirdir in the west to the upper reaches of the Euphrates and Tigris rivers in the east...

. Achaeus recovered all the districts which Attalus had gained for the Seleucids once more; but being falsely accused by Hermeias

Hermeias

Hermeias was a Carian by birth, who had raised himself to be the favourite and chief minister of Seleucus III Ceraunus , and was left at the head of affairs in Syria by that monarch when he set out on the expedition across the Taurus Mountains, in the course of which Seleucus met with his death,...

, the minister to Antiochus, of intending to revolt, he did so in self-defence, assumed the title of king, and ruled over the whole of Asia on the western side of the Taurus. As long as Antiochus

Antiochus III the Great

Antiochus III the Great Seleucid Greek king who became the 6th ruler of the Seleucid Empire as a youth of about eighteen in 223 BC. Antiochus was an ambitious ruler who ruled over Greater Syria and western Asia towards the end of the 3rd century BC...

 was engaged in the war with Ptolemy, he would not march against Achaeus; but upon the conclusion of a treaty with Ptolemy, he crossed the Taurus, uniting his forces with Attalus, and in one campaign deprived Achaeus of his dominions and took Sardis

Sardis

Sardis or Sardes was an ancient city at the location of modern Sart in Turkey's Manisa Province...

 (with the exception of the citadel). After sustaining a siege of two years, the citadel at last fell into the hands of Antiochus in 213 BC, through the treachery of Bolis (who had been employed by Sosibius

Sosibius

Sosibius was the chief minister of Ptolemy Philopator , king of Egypt. Nothing is known of his origin or parentage, though he may have been a son of Sosibius of Tarentum; nor have we any account of the means by which he rose to power; but we find him immediately after the accession of Ptolemy ,...

, minister to Ptolemy). Bolis pledged to deliver Achaeus to safety, but turned him over to Antiochus, who immediately put him to death.