 Although much of the Greek army retreated, the rearguard, formed of the Spartan and Thespian contingents, was surrounded and annihilated.The simultaneous Battle of Artemisium, consisting of a series of naval encounters, was up to that point a stalemate; however, when news of Thermopylae reached them, the Greeks also retreated, since holding the straits was now a moot point.Following Thermopylae, the Persian army proceeded to burn and sack the Boeotian cities that had not surrendered, Plataea and Thespiae, before taking possession of the now-evacuated city of Athens.