How did Cyrus successfully cross the moat in order to capture Babylon

The Euphrates River which cut through the heart of Babylon, was diverted by Cyrus and his army of the Medes. Once the waters were low enough to walk through, Cyrus leader of the Medes, crossed the moat and laid siege of city of Babylon. Babylon was vunerable to capture due to the capture of it’s King Nabonidus in the battle field and the negligence of the son King Belshazzar who left the city vunerable and without sufficient defense. Answer It appears likely that the conquest of Babylon was bloodless. The scholar, Morton Smith, believes that the Babylonian priesthood encouraged and then assisted Cyrus, because of the oppressive rule of Nabonidus, so that a seige was not necessary.