Battle of Sellasia

The Battle of Sellasia (Μάχη της Σελλασίας) took place during the summer of 222 BC between the armies of Macedon and the Achaean League, led by Antigonus III Doson, and Sparta under the command of King Cleomenes III. The battle was fought at Sellasia on the northern frontier of Laconia and ended in a Macedonian-Achaean victory.

Background
In 229 BC, the Spartan king, Cleomenes III, captured the strategically important Arcadian cities of Tegea, Mantinea, Caphyae and Orchomenus, which had aligned themselves with the powerful Achaean League, a state in Central Greece. Historians Polybius and Sir William Smith claim that Cleomenes seized the cities by treachery; however, Richard Talbert, who translated Plutarch's account of Sparta, and historian Nicholas G. L. Hammond say Cleomenes took them at their own request. Later in the year, at the behest of the ephors, Cleomenes captured the Athenaeum, which was close to Belbina. Belbina was one of the entry points in Laconia and was at the time disputed by Sparta and the city of Megalopolis.

The seizure of these cities, caused the Achaean League, a state that possessed a large area of the Peloponnese, to declare war on Sparta. Attacks by the Achaean strategos, Aratus of Sicyon, to take Tegea and Orchomenus by using night attacks failed and forced Aratus to retreat. The Spartan army of 5,000, under the command of Cleomenes, marched into Arcadia and ravaged Achaean territory before forcing a much larger Achaean army to withdraw.

Meanwhile, Ptolemy III of Egypt, who had been subsidising the Achaean League in their struggle against Macedon, decided to shift his financial support to Sparta as he saw a resurgent Sparta as a bigger threat to Macedon than a failing Achaean League. In May 227 BC, Aratus attacked the city state of Elis, which appealed to Sparta for military support. As the Achaean army was returning from Elis, they were attacked and routed by Cleomenes.

Having bribed the ephors into allowing him to continue his campaign, Cleomenes invaded Megalopolitan territory, where he was confronted by an Achaean army. After a minor setback, the Spartans rallied and destroyed the Achaean army. The demoralised Achaean League made no further efforts to attack Sparta in that year. Cleomenes was now confident enough of his strong position to start plotting against the ephors. After recruiting a few followers, he returned to Sparta with a group of mercenaries and killed all of the ephors except one, who managed to gain sanctuary in a temple. With the ephors vanquished, Cleomenes was able to initiate his social, economical and military reforms, which included land reforms, cancellation of debts and the conversion of the Spartan military into a Macedonian-styled army.

In 226 BC, Mantinea, which had been captured by the Achaeans, appealed to Cleomenes for assistance in expelling the Achaean garrison. After he removed the Achaean garrison from the city, Cleomenes move his army into Achaea in hope of drawing the Achaean army into a pitched battle. At Dyme, the Spartan army met the entire Achaean army and routed the Achaean phalanx. This crushing defeat forced the Achaeans to negotiate and Cleomenes demanded that the League be surrendered to him. However, before terms could be reached, Cleomenes became stricken by an illness and was forced to return to Sparta.

Taking advantage of the lull in the negotiations, Aratus began to negotiate with King Antigonus III Doson of Macedon. However, the majority of the League was against negotiating with the Macedonians so Aratus's plans were quashed for the time being. In a quick campaign, Cleomenes managed to capture the cities of Cleonae, Argos, Corinth, Hermione, Troezen and Epidaurus. This latest disaster forced the Achaeans to conclude an alliance with Antigonus, under which they were to give him the Acrocorinth, as well as the cities of Orchomenus and Heraea in return for his assistance against Cleomenes.

Prelude
Antigonus marched towards the Peloponnese with a large army of 20,000 infantry and 1,300 cavalry via the island of Euboea. They resorted to this after having their passage blocked by the hostile Aetolian League, who threatened to block their march if they went further south. After reaching the Isthmus of Corinth, the Macedonian army found their march halted by a series of fortifications that Cleomenes had erected across the Isthmus. Several attempts to breach the fortifications were repulsed with considerable losses.

Argos, however, revolted against Sparta and expelled their garrison with the help of some Macedonian soldiers. This defeat forced Cleomenes to abandon his position on the Isthmus and to retreat back to Arcadia. Meanwhile, Antigonus revived the Hellenic League of Phillip II of Macedon under the name of the "League of Leagues" and managed to incorporate most of the Greek city-states in this League.

Antigonus proceeded to capture several cities in Arcadia that had sided with Cleomenes. He returned to Achaea before dismissing his Macedonian troops so that they could winter at home. Around this time, Ptolemy of Egypt stopped paying subsides to Cleomenes, which left Cleomenes without money with which to pay for his mercenaries. In order to obtain money, Cleomenes began to sell helots their freedom in exchange for a sum of money.

Cleomenes became aware of the fact that Antigonus had dismissed all of his Macedonian troops and decided to launch a raid on the Achaean League. He gave the impression that he was going to raid the territory of Argos but instead switched directions and attacked Megalopolis. The Spartans managed to overrun a weak section of the fortifications and began to take over the city. The citizens of Megalopolis were not aware that the Spartans were in the city until dawn after which a rearguard action by some of the citizens allowed most of the Megalopolitans to escape. Cleomenes sent the Megalopolitans a message offering back their city if they joined his alliance but when this offer was refused, Cleomenes ordered that the city be sacked and razed.

Battle
The sack of Megalopolis came as a big shock for the Achaean League. Cleomenes followed this success up by raiding the territory of Argos, as he knew Antigonus could not resist him due to a lack of men. Cleomenes had also hoped that a raid on Argive territory would make the Argives lose faith in Antigonus because of his failure to protect their land. Walbank describes this raid as being "an impressive demonstration, but it had no effect other than to make it even more clear that Cleomenes had to be defeated in a pitched battle."

Cleomenes had taken up a strong position, placing his army across a road that followed a river running between two hills, Olympus and Eva. His army of 20,000 infantrymen was composed of Spartan hoplites, possibly Spartan pikemen (according to Plutarch, Cleomenes had armed 2,000 Lacedaemonians in the Macedonian military style), perioeci, mercenaries and about 650 cavalry. The Spartan phalanx, under the personal command of Cleomenes, made up the right wing of the battle line and was positioned on the hilltop of Olympus near Sellasia. This force was supported by a body of light infantry mercenaries. The allied troops as well as the perioeci phalanx were led by Cleomenes' brother, Eucleidas. These forces made up the left wing of Cleomenes' battle line and were positioned on Eva. The center occupied the valley and road and was made up of Spartan cavalry, supported by mercenaries. Cleomenes probably hoped that the higher tactical position his army enjoyed would compensate for his numerical inferiority. To be sure, he ordered a ditch dug and a palisade raised all along the front line.

Antigonus, for his part, arrived on the scene with a superior force of around 30,000 men, including the allied forces of the Achaean League. For the first time since the beginning of the 3rd century BC, the Macedonians arrayed against the Spartans a true national army and not one composed of mercenaries. Antigonous alone had with him 10,000 pikemen, 3,000 peltasts and 300 cavalry from Macedonia as well as 1,000 Agrianes, 1,600 Illyrians, 1,000 Galatians and 3,000 unidentified mercenaries and 300 cavalry. The allies provided him with further important contingents, the Achaeans with 3,000 infantry and 300 cavalry, the Boeotians with 2,000 infantry and 200 cavalry, the Acarnanians with 1,000 infantry and 50 cavalry, and the Epirotes with 1,000 infantry and 50 cavalry.

Antigonus placed his phalanxes facing the Lacedaemonian infantry which was arrayed at the top of the two hills, with the order to advance and take the heights. His cavalry of Macedonians, Achaeans (led by Philopoemen), Boeotians and mercenaries under the command of Alexander, were arrayed in front of the enemy cavalry in the center. The Macedonian right wing on Eva advanced against the Lacedaemonians, but was attacked from the rear by enemy light infantry that was initially arrayed with the cavalry. Assaulted both from the rear and the front, Antigonus' phalanx was hard pressed until Philopoemen, disregarding his orders, charged with his men and relieved the phalanx forcing the enemy light troops to retreat, thus ensuring victory for the Macedonians. After the battle, Antigonus praised young Philopoemen's initiative. According to Plutarch, out of 6,000 Spartans, only 200 survived, the others preferring honorable death to disgrace. Cleomenes fled to Alexandria where he stayed until his death.

Military ranks
In the Achaean League, the position of strategos was the highest. A strategos was elected annually by the Achaean ekklesia or assembly and he was the lead general of the League for the year as well as the chief magistrate. No one could hold the position for more than one year.