the Quraysh, came forward and threw down a challenge for a duel. Abu Bakr accepted the challenge but was stopped by Muhammad. Later, Abd al-Rahman approached his father and said to him "You were exposed to me as a target, but I turned away from you and did not kill you." To this Abu Bakr replied "However, if you had been exposed to me as a target I would not have turned away from you." In the second phase of the battle, Khalid ibn al-Walid's cavalry attacked the Muslims from behind, changing a Muslim victory to defeat. Many fled from the battlefield, including Abu Bakr. However, according to his own account, he was "the first to return". Battle of the Trench In 627 he participated in the Battle of the Trench and also in the Invasion of Banu Qurayza. In the Battle of the Trench, Muhammad divided the ditch into a number of sectors and a contingent was posted to guard each sector. One of these contingents was under the command of Abu Bakr. The enemy made frequent assaults in an attempt to cross the ditch, all of which were repulsed. To commemorate this event a mosque, later known as 'Masjid-i-Siddiq', was constructed at the site where Abu Bakr had repulsed the charges of the enemy. Battle of Khaybar Abu Bakr took part in the Battle of Khaybar. Khaybar had eight fortresses, the strongest and most well-guarded of which was called Al-Qamus. Muhammad sent Abu Bakr with a group of warriors to attempt to take it, but they were unable to do so. Muhammad also sent Umar with a group of warriors, but Umar could not conquer Al-Qamus either. Some other Muslims also attempted to capture the fort, but they were unsuccessful as well. Finally, Muhammad sent Ali, who defeated the enemy leader, Marhab. Military campaigns during final years of Muhammad In 629 Muhammad sent 'Amr ibn al-'As to Zaat-ul-Sallasal, followed by Abu Ubaidah ibn al-Jarrah in response to a call for reinforcements. Abu Bakr and Umar commanded an army under al-Jarrah, and they attacked and defeated the enemy. In 630, when the Muslims conquered Mecca, Abu Bakr was part of the army. Before the conquest of Mecca his father Abu Quhafa converted to Islam. Battles of Hunayn and Ta'if In 630, the Muslim army was ambushed by archers from the local tribes as it passed through the valley of