When Mardonius heard that the Allied army was on the march, he retreated into Boeotia, near Plataea, trying to draw the Allies into open terrain where he could use his cavalry.[146] The Allied army however, under the command of the Spartan regent Pausanias, stayed on high ground above Plataea to protect themselves against such tactics.[147] Mardonius ordered a hit-and-run cavalry attack on the Greek lines,[148] but the attack was unsuccessful and the cavalry commander killed.[149] The outcome prompted the Allies to move to a position nearer the Persian camp, still on high ground.[150] As a result, the Allied lines of communication were exposed. The Persian cavalry began to intercept food deliveries and finally managed to destroy the only spring of water available to the Allies.[147] The Allied position now undermined, Pausanias ordered a night-time retreat towards their original positions.[147] This went awry, leaving the Athenians, and Spartans and Tegeans isolated on separate hills, with the other contingents scattered further away, near Plataea itself.[147] Seeing that he might never have a better opportunity to attack, Mardonius ordered his whole army forward.[151][152] However, as at Thermopylae, the Persian infantry proved no match for the heavily armoured Greek hoplites,[153] and the Spartans broke through to Mardonius's bodyguard and killed him.[154] The Persian force thus dissolved in rout; 40,000 troops managed to escape via the road to Thessaly,[155] but the rest fled to the Persian camp where they were trapped and slaughtered by the Allies, thus finalising their victory.[152][156]