Khalid bin Walid: From General to Foot-Soldier
During the reign of Prophet Muhammad (صلي الله عليه وسلم), and later, the reign of Abu Bakr, the first Khalifa, may Allah be pleased with him, Khalid bin Walid, commander of the Muslim army, rocked the non-Muslim armies again and again and again and lead the Muslims to many victories. In this way, he became a fitnah–people ascribed victory to him, and not to Allah (سبحانه وتعالى).
After the battle of Yarmuk, the newly-instated Khalifa, ‘Umar ibn al-Khattab (may Allah be pleased with him) removed Khalid bin Walid from leadership of the army and instated Abu Ubaydah (RA) as the commander.