Iraq began to focus on using defense in depth to defeat the Iranians. Iraq created multiple static defense lines to bleed the Iranians through sheer size. When faced against large Iranian attack, where human waves would overrun Iraq's forward entrenched infantry defences, the Iraqis would often retreat, but their static defences would bleed the Iranians and channel them into certain directions, drawing them into traps or pockets. Iraqi air and artillery attacks would then pin the Iranians down, while tanks and mechanised infantry attacks using mobile warfare would push them back. Sometimes, the Iraqis would launch "probing attacks" into the Iranian lines to provoke them into launching their attacks sooner. While Iranian human wave attacks were successful against the dug in Iraqi forces in Khuzestan, they had trouble breaking through Iraq's defense in depth lines. Iraq had a logistical advantage in their defence: the front was located near the main Iraqi bases and arms depots, allowing their army to be efficiently supplied. By contrast, the front in Iran was a considerable distance away from the main Iranian bases and arms depots, and as such, Iranian troops and supplies had to travel through mountain ranges before arriving at the front.