Khalid ibn al-Walid was a member of the Quraysh tribe and initially fought against Prophet Muhammad, most notably turning the tide of the Battle of Uhud with a brilliant cavalry charge.
He converted to Islam around 629 and was given the title 'Sword of Allah' (Saifullah) by Muhammad.
Under the Rashidun Caliphs Abu Bakr and Umar, he led the Muslim armies to stunning victories against the Byzantine and Sasanian empires, conquering Syria and Iraq.