The Battle of Sellasia (Greek: Μάχη της Σελλασίας) took place in the summer 222 BC between the armies of Macedon and the Achaean League, lead 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.
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 Aetolian 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 N. 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 possess 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 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 appeal 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 army into a Macedonian style.
In 226 BC, Mantinea, which had been captured by the Achaean 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 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.
Antigonus marched towards the Peloponnese with a large army of 20,000 infantry and 1,300 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 they found the Macedonian army found their march halted by a series of fortification that Cleomenes had erected across the Isthmus. Several attempts to breach the fortification were repulsed with considerable losses.
However, Argos 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 many 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 Cleomenes 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 begin to take over the city. The citizens of Megalopolis did not become 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 message offering back their city if they joined this alliance but when this offer was refuse, Cleomenes ordered that the city be sacked and razed.
The capture of Megalopolis shook the Achaean League. Cleomenes set off with his army to raid the territory of Argos, knowing that Antigonus would not resist him due to a lack of men. Cleomenes also hoped that his raid would cause the Argives to lose confidence in Antigonus because of his failure to protect their territory. Walbank describes this raid as being 'an impressive demonsration, but it had no effect other than to make it even more clear that Cleomenes had to be defeated in a pitched battle.
In the summer of 222 BC, Antigonus summoned his troops from Macedon, who arrived together with other allied forces. According to Polybius, the Macedonian army consisted of: 10,000 Macedonian infantry, most of them armed as phalangites, 3,000 peltasts, 1,200 cavalry, 3,000 mercenaries, 8,600 Greek allies and 3,000 Achaean infantry, making a total of 29,200 men.
Cleomenes had fortified all the passes into Laconia with barricades and trenches before setting off with his army of 20,000 men to the pass at Sellasia, on the northern border of Laconia. Overlooking the pass at Sellasia were two hills, Evas and Olympus. Cleomenes positioned his brother, Eucleidas, with the allied troops and the Perioeci on Evas; he stationed himself on Olympus with 6,000 Spartan hoplites and 5,000 mercenaries.
When Antigonus reached Sellasia with his army, he found it well guarded and decided against storming the strong position. Instead he pitched camp near Sellasia and waited for several days. During this time, he sent scouts to reconnoiter the areas and feign attacks on Cleomenes' position.
Unable to force a move from Cleomenes, Antigonus decided to risk a pitched battle. He positioned some of his Macedonian infantry and Illyrians facing the Evas hill in an articulated phalanx. The Epirots, the Acarnanians and 2,000 Achaean infantry stood behind them as reinforcements. The cavalry took a position opposite Cleomenes' cavalry, with 1,000 Achaean and Megalopolitan infantry in reserve. Together with the rest of his Macedonian infantry and mercenaries Antigonus took his position opposite that of Cleomenes.
The battle started when the Illyrian troops on the Macedonian right wing attacked the Spartan force on Evas. The Spartan light infantry and cavalry, noticing that the Achaean infantry was not protected at the rear, launched an assault on the back of the Macedonian right wing, and threatened to rout it. However, at the critical moment, Philopoemon of Megalopolis (who later became one of the greatest heroes of the Achaean League, eventually conquering Sparta), tried to point out the danger to the senior cavalry commanders. When they did not take notice of him, Philopoemon gathered a few other cavalrymen and charged the Spartan cavalry. The Spartans attacking from the rear broke off their engagement with the enemy, which encouraged the Macedonians to charge at the Spartan positions. The Spartan left flank was eventually forced back and thrown from their position and with their commander, Eucleidas killed; they fled the field.
Meanwhile, the Macedonian phalanx on the left flank engaged the Spartan phalanx and mercenaries. During the initial assault the Macedonian phalanx gave a considerable amount of ground before its weight drove back the Spartan phalanx. The Spartans, overwhelmed by the deeper Macedonian phalanx, were routed, but Cleomenes managed to escape with a small group of men. The battle was very costly for the Spartans; most of their army was routed. Of the 6,000 Spartans that fought, only 200 were still living at the end of the battle
