Year 220 BC was a year of the pre-Julian Roman calendar. At the time it was known as the Year of the Consulship of Laevinus/Catulus and Scaevola/Philo (or, less frequently, year 534 Ab urbe condita). The denomination 220 BC for this year has been used since the early medieval period, when the Anno Dominicalendar era became the prevalent method in Europe for naming years.
With Molon occupying significant parts of the Seleucid kingdom and assuming the title of king, on the advice of his chief Minister, Hermeias, Antiochus III abandons a campaign to conquer southern Syria from Egypt. Antiochus III instead marches against Molon, defeating and killing him and his brother Alexander on the far bank of the Tigris. Antiochus goes on conquer Atropatene, the north-western part of Media.
Meanwhile, the birth of a son to Antiochus III and Laodice (daughter of Mithridates II, king of Pontus) leads Hermeias to consider getting rid of the king so that he can rule under the name of the infant son. Antiochus discovers the scheme and arranges the assassination of Hermeias.
Antiochus III's commander in Anatolia, Achaeus, having recovered all the districts which Attalus of Pergamum has gained, is accused by Hermeias, the chief minister of Antiochus, of intending to revolt. In self-defence, Achaeus assumes the title of king and rules over the Anatolian parts of the Seleucid kingdom.