One of Perseus' first acts on becoming king of Macedonia is to renew the treaty between Macedonia and Rome. In the mean time, Perseus builds up the Macedonian army and puts out feelers for creating an alliance with the Greek leagues, with his northern barbarian neighbours, and also with the Seleucid king Seleucus IV.
Antiochus manages to oust Heliodorus and takes advantage of Demetrius' captivity in Rome to seize the throne for himself under the name Antiochus IV Epiphanes.
During this period of uncertainty in Syria, the Egyptian ruler, Ptolemy VI, lays claim to Coele Syria, Palestine, and Phoenicia, which the Seleucid king Antiochus III has previously conquered. Both the Syrian and Egyptian parties appeal to Rome for help, but the Roman Senate refuses to take sides.
Timarchus is appointed governor of Media in western Persia by Antiochus IV to deal with the growing threat from the Parthians while Timarchus' brother, Heracleides, becomes minister of the royal finances.
The construction of the western front of the altar in Pergamum, Turkey begins (approximate date) and is finished in 156 BC. A reconstruction of it is now kept at the Staatliche Museen zu Berlin, Preussischer Kulturbesitz, Pergamonmuseum in Berlin.
Since the reign of the Seleucid king, Antiochus III, the Jewish inhabitants of Judea enjoy extensive autonomy under their high priest. However, they are divided into two parties, the orthodox Hasideans (Pious Ones) and a reform party that favours Hellenism. Antiochus IV supports the reform party because of the financial support they provide him with. In return for a considerable payment, he has permitted the high priest, Jason, to build a gymnasium in Jerusalem and to introduce the Greek mode of educating young people. Jason's time as high priest is brought to an abrupt end when he sends Menelaus, the brother of Simon the Benjamite, to deliver money to Antiochus IV. Menelaus takes this opportunity to "outbid" Jason for the priesthood, resulting in Antiochus IV confirming Menelaus as the High Priest.
The peace treaty at the end of the Second Punic War requires that all border disputes involving Carthage be arbitrated by the Roman Senate and requires Carthage to get explicit Roman approval before going to war. As a result, envoys from Carthage appear before the Roman Senate to request resolution of a boundary dispute with Numidia. The dispute is decided in Numidia's favour.
Antiochus IV decides to let Ptolemy VI continue as king of Egypt, but as his puppet. He does this to minimise any reaction from Rome towards his invasion. Antiochus IV then departs Egypt to deal with disturbances in Palestine, but he safeguards his access to Egypt with a strong garrison in Pelusium.
With Antiochus IV now absent from the country, the citizens of Alexandria choose Ptolemy VI's brother Ptolemy VIII Euergetes II as their king. The two Ptolemy brothers agree to rule Egypt jointly with their sister Cleopatra II and Coele Syria is invaded by the Egyptian forces.
The usurped high priest of Judea, Jason, does not abandon his claims to being the high priest which he has lost to Menelaus two years earlier. While Antiochus IV is waging war against Egypt, he succeeds in making himself master of Jerusalem once more and forces Menelaus to seek refuge in the citadel.
Philip V, king of Macedonia from 221 BC, whose attempt to extend Macedonian influence throughout Greece has occurred at a time of growing Roman involvement in Greek affairs and resulted in his military defeat by Rome (b. 238 BC)