Khalid ibn al-Walid (592–642) also known as SayfAllah al-Maslul (the Drawn Sword of Allah), was a Sahabi, a companion of the prophet Muhammad(pbuh), and one of the greatest military commanders of all time. He is noted for his military tactics and prowess, commanding the forces of Muhammad(pbuh) and those of his immediate successors of the Rashidun Caliphate; Abu Bakr and Umar. It was under his military leadership that Arabia, for the first time in history, was united under a single political entity, the Caliphate. He is one of three military generals in history to remain undefeated in battle. He has the distinction of being undefeated in over a hundred battles, against the numerically superior forces of the Byzantine-Roman Empire, Sassanid-Persian Empire, and their allies, in addition to other Arab tribes. His strategic achievements include the conquest of Arabia, Persian Mesopotamia and Roman Syria within several years from 632 to 636. He is also remembered for his decisive victories at Yamamah, Ullais, Firaz, and his tactical marvels, at the Walaja and Yarmouk. He is also one of the two military commanders, the other being Hannibal, who have successfully executed the pincer movement against a numerically superior opponent.
Khalid ibn al-Walid (Khalid son of al-Walid) was from the Meccan tribe of Quraysh, from a clan that initially opposed Muhammad(pbuh). He played a vital role in the Meccan victory at the Battle of Uhud. He converted to Islam, however, and joined Muhammad(pbuh) after the Treaty of Hudaybiyyah and participated in various expeditions for him, such as the Battle of Mutah. After Muhammad's(pbuh) death, he played a key role in commanding Medinan forces for Abu Bakr in the Ridda wars, conquering central Arabia and subduing Arab tribes. He captured the Sassanid Arab client Kingdom of Al-Hirah, and defeated the Sassanid Persian forces during his conquest of Iraq (Mesopotamia). He was later transferred to the western front to capture the Roman Syria and the Byzantine Arab client state of the Ghassanids. Even though Umar later relieved him of high command, he nevertheless remained the effective leader of the forces arrayed against the Byzantines during the early stages of the Byzantine–Arab Wars. Under his command, Damascus was captured in 634 and the key Arab victory against the Byzantine forces was achieved at the Battle of Yarmouk (636),which led to the conquest of the Bilad al-Sham (Levant). In 638, at the zenith of his career, he was dismissed from military services.
Conversion to Islam:
A peace agreement of ten years was concluded between the Muslims and Quraysh of Mecca at the Treaty of Hudaybiyyah in 628. It has been recorded that Muhammad(pbuh) told Khalid's brother, Walid bin Walid, that: "A man like Khalid, can't keep himself away from Islam for long". Walid wrote letters to Khalid persuading him to convert. Khalid, who was not unduly drawn towards the idols of the Kaaba, decided to convert to Islam and is said to have shared this matter with his childhood friend Ikrimah ibn Abi-Jahl who opposed him. Khalid was threatened by Abu Sufyan ibn Harb with dire consequences, but was restrained by Ikrimah who is reported to have said: "Steady, O Abu Sufyan! Your anger may well lead me also to join Muhammad(pbuh). Khalid is free to follow whatever religion he chooses". Some time in May 629, Khalid set out for Medina. On the way he met 'Amr ibn al-'As and Uthman ibn Talha, who were also going to Medina to convert to Islam. They arrived at Medina on 31 May 629 and went to the house of Muhammad. Khalid was received by his elder brother Walid bin Walid and was first among the three men to enter Islam.