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.