Khalid ibn al-Walid is the Greatest Military Leader Ever.
He beat the superpowers of the Romans (who conquered nearly all of Europe) and the Persians that had greater numbers and equipment with only a small rag tag band of bedouin nomads.
HE NEVER LOST.
Involved In 100 battles and over 100 duels 1 versus 1.
Never retreated.
In the battle of Yarmouk, he led the Muslim nomads of 20,000 to defeat the Romans numbering 200,000 in 6 days. The Romans never recovered after this and then proceeded to lose Jerusalem right after.
In the Battle of Battle of Firaz, he led 15,000 Muslims against 150,000 COMBINED forces of Romans, Persians and Christian Arabs and won. He was outnumbered 10:1
He actually defeated the Prophet Mohammed in war.
In the first battle ever between the Muslims and the Romans, Battle of Mu'tah, where he defeated 200,000 Roman fighters with 3,000 Muslims while Khalid Ibn Walid broke nine swords on the enemy.
Under his military leadership, Arabia became united for the first time in their history under the Caliphate.
It is said there was no part of his body that wasn't wounded, yet he never rested until his death
Showed versatility against similar nomadic troops in the Ridda wars, and against a totally different Persian enemy in Iraq and modern Iran and later against Byzantium.
Often changed losses into crushing victories.
Never ransacked the territories he invaded, sparred the lives of women, children and old people.
Captured the daugther of Emperor Heraclius of the Byzantine Empire. When asked to return by the Emperor, he said "Take her as a gift, there shall be no ransom."
In 638, at the zenith of his career, he was dismissed from military services.
"Is the standard of this army a black one? Is the commander of this army a tall, powerfully built, broad shouldered man with a large beard and a few pock marks on his face? Then beware of fighting this army. " Byzantine priest. (633 A. D)