The First Syrian War was one of a series of conflicts between Ptolemaic Egypt and the Seleucid Empire. There had been tension between the two empires over the status of southern Syria since the battle of Ipsus (301 BC). In the treaty (303 BC) that had created the victorious coalition that won at Ipsus, Ptolemy I had been promised all of Syria, but he had not sent troops to Ipsus, and in the distribution of land after the battle, Syria had been allocated to Seleucus.
Ptolemy had reacted in 301 by occupying most of Syria south of Damascus, as well as much of Phoenicia. The Ptolemies later claimed Syria as far as Damascus. This was a traditional Egyptian policy, and was aimed at providing security for the Egyptian heartland. At the same time the Seleucids claimed all of southern Syria, for similar reasons – the heartland of their empire was based around northern Syria and eastern Asia Minor.
As long as Ptolemy I and Seleucus I were alive the two men avoided war between their empires, but in 283 Ptolemy died of natural causes (the only one of the successors of Alexander the Great to do so), and in 280 Seleucus was murdered. The first fighting between the two empires appears to have followed almost immediately (Damascene War, 280-279 BC), probably fought in Ionia, around the city of Miletus.
Seleucus’s heir Antiochus I was faced with several enemies during this period. He had been at war with Antigonus, was facing a rebellion in the Seleucis, his family’s homeland, and in 279 BC the Gauls invaded Macedonia, before moving on to Greece and then later into Asia Minor, which they reached by 277. In face of the Gallic threat Antiochus and Antigonus had made peace (probably 279 BC), and agreed spheres of influence – Antigonus would have Macedonia and Greece, Antiochus would have Thrace and all areas east.
This alliance posed a threat to Ptolemaic Egypt, and her ambitions. Ptolemy II possessed the powerful Egyptian fleet, and ambitions to create a maritime empire in the Aegean Sea, where he already had allies at Miletus.
The First Syrian War broke out in 276. Antiochus had put down the rebellion in the Seleucis, and then moved west to deal with the Gallic threat. He had spent the winter of 277-6 at Sardes, in Lydia, in preparation for a campaign against the Gauls. This plan had to be abandoned, when in the spring of 276 Ptolemy II launched an invasion of central Syria, seizing Damascus and the Marsyas Valley (north of Damascus).
Antiochus responded vigorously. He marched east into Syria, defeated the Egyptians and reoccupied Damascus. He also appears to have begun a siege of Miletus, by land and sea, possibly under the command of his son Seleucus, who he had left in Asia Minor. The naval element of that siege was broken by the Egyptian fleet under Callicrates of Samos (probably in 275), but the land element continued and may even have succeeded (if so, the city was lost again in Eumenes’ War).
In 275 Antiochus turned back to the Gauls. The revolt in the Seleucis has lost him his war elephants, and so he had turned east. His empire still stretched east almost to India, and he had ordered the general in charge of Bactria to obtain Indian elephants. These reached Syria in the spring of 275. Antiochus crossed back into Asia Minor, and inflicted a defeat on the Gauls at the battle of the Elephants. This ended the direct Gallic threat to his kingdom, although the Gauls themselves remained in Asia Minor, settling in Galatia. This was the highpoint for Antiochus. He gained the cult name “Soter” (Saviour), and was praised for restoring peace.
A new figure now entered the scene. This was Arsinoe, sister of Ptolemy II, widow of Lysimachus of Macedonia, and briefly wife of Ptolemy Keraunos. After being betrayed by Keraunos, she fled to Samothrace and then to her brother’s court in Egypt. At some time between 277 and 275, Arsinoe and Ptolemy II were married. She adopted his son (late Ptolemy III), he adopted her son Ptolemaeus. This controversial marriage soon proved to be a great success. Arsinoe became co-ruler of Egypt, and after her death joined the pantheon of Egyptian gods. By the end of 275 Arsinoe also seems to have taken over control of the war.
Antiochus appears to have had a grand plan to invade Egypt in 274. He married his daughter to Ptolemy’s half brother Magas, governor of Cyrenaica, west of Egypt. Magas declared himself independent of Egypt, and in 274 launched an invasion of Egypt that came close to reaching Alexandria. He was aided by a mutiny amongst Ptolemy’s Gallic mercenaries. Arisnoe responded by encouraging a Libyan invasion of Cyrenaica, which forced Magas to return west to secure his own base. The Gallic mercenaries were trapped on an island and their revolt put down.
The real key to the Egyptian victory was their fleet. In 274 that fleet was sent to attack the coast of Asia Minor, directly threatening Antiochus in his Cilician heartland. Any hope Antiochus may have had of receiving help from Macedonia ended when Ptolemy and Arsinoe funded an invasion of Macedonia by Pyrrhus of Epirus.
The Egyptian invasion of Asia Minor was a great success. Callicrates captured a large part of the coastline, forcing Antiochus to admit defeat. Egypt gained western Cilicia and a string of possessions that included southern Lycia, Caunus, Halicarnassus, Myndus and Cnidus. Ptolemy probably also ended the war in possession of Miletus. In Syria he gained all of Phoenicia and the Marsyas valley, but not Damascus.
In the aftermath of the war, Arsinoe began to plan an attack on Macedonia, where her son Ptolemaeus had a good claim to the throne. However, before her plans could be put into action, Arisnoe died (270 BC). The resulting Chremonidean War ended in victory for Antigonus, and an alliance between Antigonus and Antiochus against Ptolemy.