Alexander I Theopator Euergetes, surnamed Balas (), was the ruler of the Seleucid Empire from 150/Summer 152 – August 145 BC. Picked from obscurity and supported by the neighboring Roman-allied Kingdom of Pergamon, Alexander landed in Phoenicia in 152 BC and started a civil war against Seleucid King Demetrius I Soter. Backed by mercenaries and factions of the Seleucid Empire unhappy with the existing government, he defeated Demetrius and took the crown in 150 BC. He married the princess Cleopatra Thea to seal an alliance with the neighboring Ptolemaic kingdom. His reign saw the steady retreat of the Seleucid Empire's eastern border, with important eastern satrapies such as Media being lost to the nascent Parthian Empire. In 147 BC, Demetrius II Nicator, the young son of Demetrius I, began a campaign to overthrow Balas, and civil war resumed. Alexander's ally, Ptolemaic king Ptolemy VI Philometor, moved troops into Coele-Syria to support Alexander, but then switched sides and threw his support behind Demetrius II. At the Battle of the Oenoparus River in Syria, he was defeated by Ptolemy VI and he died shortly afterward. Life Origins and mission to Rome Alexander Balas claimed to be the son of Antiochus IV Epiphanes and Laodice IV and heir to the Seleucid throne. The ancient sources, Polybius and Diodorus say that this claim was false and that he and his sister Laodice VI were really natives of Smyrna of humble origin. However, Polybius became friends with Balas's rival King Demetrius I when both were hostages in Rome, so Polybius is not an unbiased source on this matter. Modern scholars disagree about whether the story of Attalus finding a commoner who looked the part is true or was propaganda put about by Alexander's opponents. According to Diodorus, Alexander was originally put forward as a candidate for the Seleucid throne by Attalus II of Pergamum. Attalus had been disturbed by the Seleucid king Demetrius I's interference in Cappadocia, where he had dethroned king Ariarathes V. Boris Chrubasik is sceptical, noting that there is little subsequent evidence for Attalid involvement with Alexander. However, Selene Psoma has proposed that a large set of coins minted in a number of cities under Attalid control in this period was produced by Attalus II in order to fund Alexander's bid for the kingship. Alexander and his sister were maintained in Cilicia by Heracleides, a former minister of Antiochus IV and brother