Khalid ibn al-Walīd (Arabic: خالد بن الوليد; 592--642) also known as SayfAllah al-Maslul ( the drawn Sword of Allah ), was a Sahabi,a companion of Prophet Muhammad(saws),astute in the art of war and one of the greatest tacticians in history.He is noted for his military tactics and prowess,commanding the forces of Prophet 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 the few military generals in history who have remained undefeated in battle their entire life. 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 was from the Meccan tribe of Quraysh, from a clan that initially opposed Muhammad. He played a vital role in the Meccan victory at the Battle of Uhud. He converted to Islam, however, and joined Muhammad after the Treaty of Hudaybiyyah and participated in various expeditions for him, such as the Battle of Mu'tah. After Muhammad's 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 service.