Alexander was commander of the cavalry

Cavalry

Cavalry or horsemen were soldiers or warriors who fought mounted on horseback. Cavalry were historically the third oldest and the most mobile of the combat arms...

 in the army of Antigonus III Doson

Antigonus III Doson

Antigonus III Doson was king of Macedon from 229 BC to 221 BC. He belonged to the Antigonid dynasty.-Family Background:He was a grandson of Demetrius Poliorcetes and cousin of Demetrius II, who after the latter died in battle and rescued Macedonia and restored Antigonid control of Greece...

 during the war against Cleomenes III

Cleomenes III

Cleomenes III was the King of Sparta from 235-222 BC. He succeeded to the Agiad throne of Sparta after his father, Leonidas II in 235 BC.From 229 BC to 222 BC, Cleomenes waged war against the Achaean League under Aratus of Sicyon. Domestically, he is known for his attempt to reform the Spartan state...

 of Sparta

Sparta

Sparta or Lacedaemon, was a prominent city-state in ancient Greece, situated on the banks of the River Eurotas in Laconia, in south-eastern Peloponnese. It emerged as a political entity around the 10th century BC, when the invading Dorians subjugated the local, non-Dorian population. From c...

. He fought against Philopoemen

Philopoemen

Philopoemen , was a skilled Greek general and statesman, who was Achaean strategos on eight occasions....

, then a young man, whose prudence and valor forced him to a disadvantageous engagement at Sellasia. This Alexander is probably the same person as the one whom Antigonus

Antigonus III Doson

Antigonus III Doson was king of Macedon from 229 BC to 221 BC. He belonged to the Antigonid dynasty.-Family Background:He was a grandson of Demetrius Poliorcetes and cousin of Demetrius II, who after the latter died in battle and rescued Macedonia and restored Antigonid control of Greece...

, as the guardian of Philip (son of Demetrius II of Macedon

Demetrius II of Macedon

Demetrius II Aetolicus son of Antigonus Gonatas and Phila, reigned as king of Macedonia from the winter of 239 to 229 BC. He belonged to the Antigonid dynasty and was born in 275 BC. There is a possibility that his father had already elevated to him to position of power equal to his own before his...

), had appointed commander of Philip's body-guard, and who was slandered by Apelles

Apelles

Apelles of Kos was a renowned painter of ancient Greece. Pliny the Elder, to whom we owe much of our knowledge of this artist rated him superior to preceding and subsequent artists...

. Subsequently he was sent by Philip as ambassador to Thebes

Thebes, Greece

Thebes is a city in Greece, situated to the north of the Cithaeron range, which divides Boeotia from Attica, and on the southern edge of the Boeotian plain. It played an important role in Greek myth, as the site of the stories of Cadmus, Oedipus, Dionysus and others...

, to persecute the Macedonian Megaleas

Megaleas of Macedon

Megaleas was the royal secretary to Antigonus III of Macedon, who appointed him, by his will, to the same office under Philip V, his ward and successor . Megaleas was entirely under the influence of the advisor Apelles, and readily entered into his treasonable designs , to baffle the operations of...

. Polybius

Polybius

Polybius , Greek ) was a Greek historian of the Hellenistic Period noted for his work, The Histories, which covered the period of 220–146 BC in detail. The work describes in part the rise of the Roman Republic and its gradual domination over Greece...

states that at all times he manifested a most extraordinary attachment to his king.