The Achaean League (Greek: κοινὸν τῶν Ἀχαιῶν) was a Hellenistic era confederation of Greek city states on the northern and central Peloponnese, which existed between 280 BCE and 146 BCE. The league was named after the region of Achaea.
The regional Achaean League was reformed in 281/0 BCE (on the basis of a looser alliance of the founding city-states extending back to the 5th century BCE), and soon expanded beyond its Achaean heartland. It was first joined by the city of Sicyon in 251 BCE, which provided it with its first great leader, Aratus of Sicyon. The League soon grew to control much of the Peloponnesus, considerably weakening the Macedonian hold on the area. It acquired Corinth in 243 BCE, Megalopolis in 235 BCE and Argos in 229 BCE. The increased size of the league meant a bigger citizen army and more wealth, which was used to hire mercenaries. However the league soon ran into difficulties with the revived Sparta of Cleomenes III. Aratus was forced to call in the aid of the Macedonian King, Antigonus Doson, to defeat Cleomenes in Sellasia. Antigonus re-established Macedonian control over much of the region.
In 220 BCE, the Achaean League entered into a war against the Aetolian League, which was called "the second Allied War". The young king Philip V of Macedon sided with the Achaeans and called for a Panhellenic conference in Corinth, where the Aetolian aggression was condemned.
After Aratus's death, however, the League was able to reap much of the benefits of Macedon's defeat by Rome in 197 BCE. Under the leadership of Philopoemen, the League was able to finally defeat a heavily weakened Sparta and take control of the entire Peloponnesus.
The League's dominance was not to last long, however. During the Third Macedonian War (171–168 BCE), the League flirted with the idea of an alliance with Perseus, and the Romans punished it by taking several hostages to ensure good behavior, including Polybius, the Hellenistic historian who wrote about the rise of the Roman Republic. In 146 BCE, the league erupted into an open revolt against Roman domination, the Achaean War. The Romans under Lucius Mummius defeated the Achaeans at the Battle of Corinth, razed Corinth and dissolved the League. G.T Griffith has written that Achaean War was a hopeless enterprise for the Achaeans, badly led and backed by no adequate reserves of money or men. Lucius Mummius received the agnomen Achaicus ("conqueror of Achaea") for his role.
Below are the original Peloponesian members, except the ancient regions of Sparta, Elis and Messenia. Later Hypana in Elis, Corone, Messene, Sparta and Pagae in Attica were joined by conquest. For the reported Elisphasii: possibly this word ought to be Helissonii, for the name Elisphasii occurs nowhere else in ancient history. In 223 BCE Megara in Attica deserted the Achaean League and joined the Boeotian Confederacy.
Besides many city-states on the Mainland joining the Achaean Federation, certain Mediterranean island city-states also became part of the federation. For example, Kydonia on Crete joined at some time after 219 BCE.
The Achaean army was an army of the traditional hoplite type. From the 270s BCE onwards however, much like the rest of Greece, the emergence of the Celtic shield known as the thureos was incorporated into Greek warfare and a new type of troop was developed. Reforming their troops into thureophoroi, the Achaean army was now composed of light troops. The thureophoroi were a mixture of evolved peltasts and light hoplites, carrying the thureos shield, a thrusting spear and javelins. Plutarch tells of how they could be effective at a distance, but in close combat the narrow thureos shield disadvantaged them. He also describes how they would form a formation of sorts, but it would be ineffective, as it would not have inter-locked shields or a ‘leveled line of spears’.
Aratus, one of the major Achaean strategoi and statesmen was known for his use of light forces for irregular operations, a type of warfare suited to the thureophoroi but not suited to operations in the open field. The League in 217 BCE decided to maintain a standing force of 8,000 mercenary foot and 500 mercenary cavalry, added to a picked citizen force of 3,000 infantry and 300 cavalry, of which 500 foot and 50 horse would come from Argos and the same amount from Megalopolis. Aratus also obtained 500 foot and 50 horse each from Taurion and the Messenians for defence of parts of the League open to attack via Laconia. The citizen infantry would have been armed as thureophoroi, apart from the citizen light troops who would have been archers and slingers etc. This picked citizen force may well have existed before these so-called reforms, at least on an official basis, as we know of a similar elite force of the same size as Sellasia in 222 BCE.
However, it was the Achaean general Philopoemen in 208 BCE who changed the Achaean fighting style and weaponry to the Macedonian fashion. This was due to the influence of Philip V of Macedon, who supported Philopoemen. Philip, at the time of Philopoemen's reforms, was in a full-scale war and could not support or finance the League. He realized that the League had to become militarily self-sufficient but also kept in the Macedonian sphere, lest the League join Macedon's rivals. Philip V probably supported Philopoemen for strategos for the year 208/07 BCE and in doing so was able to get what he wanted. According to Plutarch, Philopoemen ‘persuaded them to adopt long pike and heavy shield instead of spear and buckler, to protect their bodies with helmets and breastplates and greaves, and to practise stationary and steadfast fighting instead of the nimble movements of light-armed troops’.
These ‘reforms’ were not necessarily new to some of the constituent cities of the League, the city of Megalopolis had been given bronze shields and armed in the Macedonian fashion by Antigonus Doson for the Sellasia campaign many years before. Philopoemen then trained the new army how to fight with the new weapons and tactics and how to co-ordinate them with a new mercenary corps that was hired. He spent nearly 8 months in his term as strategos visiting, training and advising cities in this capacity. At the Battle of Mantinea in 207 BCE the Achaean phalanx was positioned with intervals between the companies with lighter troops. This was obviously a major attempt by Philopoemen to increase the flexibility of his phalanx.
He too may have picked this tactic up from his experience at the Battle of Sellasia, where the phalanx of Antigonus Doson was also divided up with light/medium troops in between them. As well as reforming and re-organizing the infantry, Philopoemen also did this with the citizen cavalry. The cavalry was recruited, much like in other Greek states, from the rich and noble classes. Philopoemen organized the cavalry in lochoi, which usually in ancient military treatises means ‘files’, most probably of 8 men, grouped into dilochiai, a formation of double-files of 16 and so forth. However by the time of the Achaean war in the 140s BCE the League's army had decreased in strength and efficiency. The League was even reduced to freeing and arming 12,000 slaves. This was probably due to the second century BCE decline in population. This may well account for the increased hiring of mercenaries, especially Cretans and Thracians.
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