April-June 222: Comes to power after the assassination of his elder brother, Seleucus III Keraunos, who has unsuccessfully tried to recover territories that had been lost to king Attalus I Soter of Pergamon
Antiochus' general Achaeus has more success, but proclaims himself king
222-220: Antiochus visits Nisibis and suppresses the revolt of Molon in Media and Persis
219: outbreak of the Fourth Syrian War against king Ptolemy IV Philopator; Antiochus reconquers Seleucia (the port of Antioch, which had been conquered by Ptolemy III in the Third Syrian War) and proceeds to the south, capturing Tyre
217, 13 June: Ptolemy's army defeats the Seleucid army at Raphia with an army that consists partly of Egyptian soldiers
October 217: peace is concluded; the Seleucid Empire keeps Seleucia
216: Alliance with Attalus against Achaeus.
216-213: Antiochus defeats Achaeus and captures Sardes
212-205: Antiochus reconquers the independent kingdoms in Parthia (Arsaces II) and Bactria and Gandara; he is called Megas, "the great"
205: Ptolemy IV Philopator falls ill; Antiochus and Philip V of Macedonia agree to attack Egypt
202, May: Outbreak of the Fifth Syrian War; renewed attempt to conquer southern Syria
200: Battle of Paneion: Ptolemy V loses his Asian territories; Antiochus' daughter Cleopatra Syra marries to the Egyptian king
Rome declares war against Macedonia (which leaves the war against the Ptolemies) and orders Antiochus to keep their hands off Egypt, which is vital for Rome's food supply
199-197: Antiochus cancels his invasion of Egypt, and instead attacks Ptolemaic possessions in Cilicia and Lycia
Antiochus III the Great
196: Crown-prince Antiochus appointed as successor; he marries his sister Laodice IV
196: Conquest of Thrace, which is governed by Antiochus' son Seleucus
192-188: Syrian War against Rome and its allies Pergamon and Rhodos; the Carthaginian general in Seleucid service, Hannibal Barca, and Antiochus are defeated
191: Battle of Thermopylae; marriage to Euboea of Chalcis
190: Battle of Magnesia
189: Seleucus made co-ruler; he probably marries his sister Laodice IV, widow of Antiochus
Peace of Apamea: cedes all territory north of the Taurus to the Roman ally Pergamon and agrees to pay an indemnity to Rome; his youngest son Antiochus is sent to Italy as hostage
