The Thessalian League (Thessalian Aeolic: , Koinòn toûn Petthaloûn; Attic: , Koinòn tôn Thettalôn; Ionic and Koine Greek: , Koinòn tôn Thessalôn) was a koinon or loose confederacy of feudal-like poleis and tribes in ancient Thessaly, located in the Thessalian plain in Greece. The seat of the Thessalian League was Larissa. Organization and Civil War The history of the Thessalian League can be traced back to the rule of king Aleuas, a member of the Aleuadae clan. One source states that it was under Aleuas that Thessaly was divided into four regions. Some time after the death of Aleuas, it is believed that the Aleuadae split into two families, the Aleuadae and the Scopadae. The former were based in the city of Larissa, which later became the capital of the League. The two families formed two powerful aristocratic parties and bore considerable influence over Thessaly. Jason and Macedon A lack of records makes it difficult to have any details of Thessalian life or politics until the 5th century BCE, when records discuss the rise of another Thessalian family—the dynasts of Pherae. The dynasts of Pherae gradually rose to hold great power and influence over the Thessalians, challenging the power of the Aleuadae. By 374 BCE, the Pherae and the Aleuadae were united with the common, agricultural population of Thessaly by Jason of Pherae. Jason's military organization and work to unify the state challenged the Macedonian influence over Thessaly. Macedonia had left a legacy of pitting Thessalian cities against one another to prevent the rise of a powerful national state. To this end, King Archelaus of Macedonia had seized border provinces of Thessaly for substantial periods and taken sons of Thessalian aristocrats as hostages. However, according to one source, “Jason’s army was said to number eight thousand cavalry and twenty thousand hoplite mercenaries, a force large enough to encourage Philip’s father to seek a nonaggression pact with him.” The late fourth and early third centuries witnessed uneasy peace, which were punctuated by the emergence of civil war. While Sparta established dominance elsewhere in Greece, Jason strengthened the Thessalian League and made alliances with Macedon and the Boeotian League (374 BCE). His leadership gave the League unity and power. In 370 BCE, while Thessaly was still preoccupied with the Macedonian intervention, Jason was assassinated and replaced by his nephew Alexander II, who displayed outrageous tyrannical behavior. As a result, the traditional aristocratic