Another remarkable strategy developed by Al-Muthanna and later followed by other Muslim generals was not moving far from the desert so long as there were opposing forces within striking distance of its rear. The idea was to fight the battles close to the desert, with safe escape routes open in case of defeat. The desert was not only a haven of security into which the Sassanid army and Byzantine army would not venture, but also a region of free, fast movement in which their camel mounted troops could move easily and rapidly to any destination that they chose. Following this same strategy during the conquest of Iraq and Syria, Khalid ibn Walid did not engage his army deep into Iraq and Syria until the opposing army had lost its ability to threaten his routes to the desert. Another possible advantage of always keeping a desert at the rear was easy communication and reinforcement.