The next year, Abu Sufyan, the famous long-lived enemy of Islam, again attacked the Muslims at Uhud. Hamzah, the first flag-bearer of Islam and uncle of the Prophet, was killed in action. In spite of strict instructions from the Prophet, a few Muslim soldiers deserted their post when victory was in sight. This changed the course of the battle. Khalid ibn al-Walid attacked the Prophet and the grave situation was saved by the timely arrival of All. The enemies ran away and the issue was decided. Muhmmmad was deeply grieved at the death of Hamzah
source : http://imamalinet.net