("kings"). It was Aleuas Pyrrhos ("the Red") who cemented the aristocracy's predominance by reforming the Thessalian League on the basis of the "tetrads" (quadripartite division), linking it with the noble-controlled kleroi ("land lots") obliged to supply 40 horsemen and 80 infantrymen each. Traditionally, the office of tagus has been regarded as the senior magistrate of the Thessalian League; more recent studies however regard the tagus as a purely local official, and suggest the tetrarches as the head of the League. Classical period In the summer of 480 BC, the Persians invaded Thessaly. The Greek army that guarded the Vale of Tempe evacuated the road before the enemy arrived. Not much later, Thessaly surrendered. The Thessalian family of Aleuadae joined the Persians. In the Peloponnesian War the Thessalians tended to side with Athens and usually prevented Spartan troops from crossing through their territory with the exception of the army of Brasidas. In the 4th century BC Thessaly became dependent on Macedon. In the 2nd century BC, as with the rest of Greece, Thessaly came under the control of the Roman Republic. Roman period From 27 BC it formed part of the Roman province of Achaea, with capital at Corinth. In the reign of Emperor Antoninus Pius (), Thessaly was separated from Achaea and given to the province of Macedonia; eventually it became a separate province. In the new administrative system as it evolved under Diocletian () and his successors, Thessaly was a separate province within the Diocese of Macedonia, in the praetorian prefecture of Illyricum. With the division of the Roman Empire in 395, Thessaly remained as a part of the East Roman (Byzantine) Empire. Being far from the Empire's frontiers, and of little strategic importance, Greece lacked any serious fortifications or permanently stationed garrisons, a situation that lasted until the 6th century and led to much devastation by barbarian raids. Thus in 395–397, as most of Greece, Thessaly was occupied by the Visigoths under Alaric, until they were driven out by Stilicho. The Vandals under Geiseric raided the coasts of Greece in the period 466–475, and in 473 the Ostrogoths under Theodemir advanced into Thessaly and captured Larissa before Emperor Leo I gave in and allowed him and his people to settle in Macedonia. Under Theodemir's son, Theodoric the Great, the Ostrogoths once more invaded Thessaly in 482, until they left for Italy in 488. According to the Synecdemus, in