Khalid ibn al-Walid was the commander who beat the Byzantine army at Yarmouk in 636 and the Sasanians in Mesopotamia before it, and who was dismissed by the caliph Umar at the height of his success.
Khalid ibn al-Walid is the most successful field commander of the early Islamic conquests and one of the very few figures of the period whose military reputation is not seriously disputed by anyone.
He appears first on the other side. At Uhud in 625 he commanded the Meccan cavalry that turned the Muslim flank and converted a Muslim victory into a defeat — the only real reverse Muhammad suffered. He converted in 629 and was given command almost immediately.
Between 632 and 638 he commanded in the Ridda wars in Arabia, then in Mesopotamia against the Sasanians, then in Syria against the Romans, where Yarmouk is his and the archive's reason for the article. In 638 the caliph Umar dismissed him, and he never held command again.
The sources are unanimous that he was fast, aggressive and willing to take risks that a more careful commander would not, and that this is why he kept winning. They are also clear that he was hard, and in at least one case that this became a scandal.
The epithet Sayf Allah al-Maslul — "the drawn sword of God" — is attributed to Muhammad after Mu'ta, where Khalid took over from three successive commanders who had been killed and got the army out. Whether the phrase is authentic or attached later, it stuck, and it is how he is known.
The killing of Malik ibn Nuwayra during the Ridda wars, and Khalid's marriage to his widow immediately afterwards, was a scandal at the time and remains one. Abu Bakr declined to punish him, reportedly saying that he would not sheathe a sword God had drawn. Umar did not agree, and remembered.
The crossing from Iraq to Syria in 634 is the operation his reputation is built on. Ordered west to reinforce the Syrian front, he took a route across the desert that the sources describe in circumstantial and partly incredible detail, including camels killed and used as water stores.
The details are unverifiable and the marches described are at the edge of possibility, so the archive states the outcome rather than the legend: he arrived in Syria with an intact force at a moment when nobody expected him, and the campaign began going the Muslims' way immediately afterwards.
Damascus fell in 634. The Byzantines spent the next two years assembling the field army that would settle the matter, and Khalid — nominally under Abu Ubayda's overall command, but effectively directing the fighting — met it at the Yarmouk.
The battle lasted several days in August 636 and was decided by cavalry. Khalid concentrated the Muslim horse into a single mobile reserve instead of splitting it between the wings, which let him restore whichever part of his line was breaking and then, on the last day, take the Byzantine army in the flank and drive it against broken ground.
The Byzantine force was larger, was a coalition of Roman regulars, Armenians and Ghassanid Arabs with divided command, and had no comparable reserve. When it broke it could not disengage.
The strategic result was immediate: Heraclius abandoned Syria, and no Roman army came back. Eight years after winning a twenty-six-year war against Persia, the empire had lost its richest provinces to an opponent it had barely registered.
In 638 Umar removed him from command. The stated reasons vary — a gift of money to a poet, an accounting question, a general insistence on discipline — and none of them are convincing on their own.
The reason usually offered, and the one the archive finds most plausible, is political. Khalid had become the person the armies believed won the battles, and Umar wanted it understood that God won them and the caliph directed them. A commander of that stature was a structural problem regardless of loyalty, and Khalid was not obviously easy to control.
He accepted it, which is itself notable, and lived out his last four years without a command. Umar is reported to have said after his death that he had been unjust to him.
His campaigns are studied as military history in a way that little else from the period is, and the modern reputation is if anything inflated by that: the sources for his battles are late, formulaic and fond of him, and reconstructing what happened tactically at Yarmouk involves more inference than most accounts admit.
What is not in doubt is the outcome. The Levant changed hands permanently in his campaigns, and the Byzantine Empire that appears everywhere else in this archive — the one fighting on two fronts from a shrunken Anatolian base — is the empire his victories created.
The mosque at Homs that holds his reputed tomb was rebuilt in the early twentieth century on an Ayyubid foundation and remains a major shrine.