He separated all the infirm and feeble portion of the army from the rest, and informed them that he was going that night on a short expedition with the main body of the troops, and that, while he was gone, they were to remain and defend the camp. He ordered the men to build the camp fires, and to make them larger and more numerous than common, and then had the asses tied together in an unusual situation, so that they should keep up a continual braying. These sounds, heard all the night, and the light of the camp fires, were to lead the Scythians to believe that the whole body of the Persians remained, as usual, at the encampment, and thus to prevent all suspicion of their flight. Toward midnight, Darius marched forth in silence and secrecy, with all the vigorous and able-bodied forces under his command, leaving the weary, the sick, and the infirm to the mercy of their enemies. The long column succeeded in making good their retreat, without exciting the suspicions of the Scythians. They took the route which they supposed would conduct them most directly to the river. When the troops which remained in the camp found, on the following morning, that they had been deceived and abandoned, they made signals to the Scythians to come to them, and, when they came, the invalids surrendered themselves and the camp to their possession. The Scythians then, immediately, leaving a proper guard to defend the camp, set out to follow the Persian army. Instead, however, of keeping directly upon their track, they took a shorter course, which would lead them more speedily to the river. The Persians, being unacquainted with the country, got involved in fens and morasses, and other difficulties of the way, and their progress was thus so much impeded that the Scythians reached the river before them. They found the Ionians still there, although the two months had fully expired. It is possible that the chiefs had received secret orders from Darius not to hasten their departure, even after the knots had all been untied; or perhaps they chose, of their own accord, to await their sovereign's return. The Scythians immediately urged them to be gone. "The time has expired," they said, "and you are no longer under any obligation to wait. Return to your own country, and assert your own independence and freedom, which you can safely do if you leave Darius and his armies here."