Battle of Sellasia The Battle of Sellasia ( ) 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 Galatia ns 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 . Notes . 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 .