The Battle of Yarmouk
On 20th of the Islamic month of Rajab in 13 AH, the Battle of Yarmouk broke out between the Arab army and the forces of Byzantine or the Eastern Roman Empire, ending six days later in a decisive victory for Muslims. The battle consisted of a series of seesaw engagements near the Yarmouk River, along what is today the border between Syria and Jordan, south-east of the Sea of Galilee, 65 km from the Golan Heights. It is regarded as one of the most decisive battles in military history, and it marked the first great wave of Muslim conquests, ending the long sway of the then superpowers, the Romans and the Persians.
In order to check the Muslim advance, Emperor Heraclius had entered into an alliance with Emperor Yazdegird III of Sassanid Iran, and sent a massive army made up of Slavs, Greeks, Franks, Georgians, Armenians and Christian Arabs. The Muslim tactic by sending a separate force to Iraq to confront the Sassanids, however, thwarted this alliance against Islam from taking practical shape. Thus the total defeat of the numerically superior Roman army by the lightly armed Muslims saw the fall of Damascus as well, and a year later led to the liberation of Bayt al-Moqaddas without bloodshed by the Muslims, who also rapidly took over Egypt and Libya.
The emergence of Muslims on the world scene came only six years after Heraclius had succeeded in reclaiming Egypt and the Levant from the Persians, in a series of see-saw battles fought for over two decades throughout West Asia, North Africa and Eastern Europe, including Mesopotamia, the Caucasus, Anatolia, and even before the walls of Constantinople itself. The advent of Islam completely changed the world map with the entire Sassanid Empire and more than half of the whole Roman Empire disappearing forever.
An important point to note is that the Commander of the Faithful, Imam Ali (AS), who led the Muslims to victory in almost all the battles imposed upon Prophet Mohammad (SAWA) by the Arab and Israelite disbelievers, did not participate in the Roman and Persian campaigns, which were led by the neo Muslim hitherto pagan Arabs subdued by his flashing scimitar, the Dhu’l-Feqar.
Some 25 years later when these same arrogant victors of the wars against the Romans and the Persians, like Zubayr ibn Awam, Amr ibn Aas, Mu’awiyya ibn Abu Sufyan and others, tried to stir up sedition amongst Muslims in Iraq and Syria (the former Sassanid and Byzantine heartlands), Imam Ali (AS) personally assumed command and once again unsheathed the Dhu’l-Feqar to decisively defeat them. For instance, Amr ibn Aas, who used to boast of conquering Egypt, ignominiously denuded himself In Siffeen while fleeing in order to escape certain death at the hands of the Prophet’s righteous heir.