Hell only time they can win a war is when they declare it on another Muslim nation. Even then, as in Iran vs Iraq, sometimes neither one wins. Recent history shows us lessons of Arab nations being gone thru like soft cheese (Gulf War, Yom Kippur War, 7 day war)
Most of tough troops of Caliphs were Turks. Since the 10the century on, all wars of Mid-East muslims were fought by Turkish slave soldiers. They were neither Arabs nor Persians. The famous defeat of Mongols by muslims was by Mamelukes of Egypt, another group of Turkish slave soldiers settled in Egypt. It was a battle between two groups of steppe nomads from Central Asia. Without the help of Turks, muslim empire would had been gone much earlier.