Croesus began the campaign with an invasion of Cappadocia, crossing the Halys and capturing Pteria, then capital of the district and formidable as a fortress; The city was sacked, and the inhabitants enslaved.[3] Meanwhile, Cyrus had advanced to halt the Lydian incursion, and the armies met in the vicinity of the fallen city. The battle appears to have been fierce, but indecisive; Both sides sustained considerable casualties; in the aftermath, the outnumbered Croesus withdrew across the Halys. The retreat of Croesus is represented by Herodotus as a strategic decision to suspend operations until their armies were more evenly matched, by arrival of reinforcements from his allies the Babylonians, the Egyptians and particularly the Spartans.[4] Though losses were more or less equal, Croesus apparently thought he had inflicted sufficiently heavy losses on the Persians to cripple Cyrus for the winter, as he disbanded his army shortly after reaching his own territory.[5]