On March 13, 624, in the Battle of Badr, Muhammad's Muslim forces won a significant victory over the Meccan army. From the article:
"Battle of Badr | Summary
Battle of Badr, (624 ce), in Islamic history, first military victory of the Prophet Muhammad. It seriously damaged Meccan prestige while strengthening the political position of Muslims in Medina and establishing Islam as a viable force in the Arabian Peninsula. The rise of Islam against the Pagan tribes of Mecca was a vital development in military history, as well as in the history of religion and society. The Prophet Muhammad was a skilled war leader as well as the founder of a faith, and at Badr his religion was spread by the sword.
The Battle of Badr was a key moment in Muhammad’s armed struggle against Mecca’s pagan tribes. In 622 Muhammad and his followers had emigrated from Mecca to Medina. From his new base Muhammad began raiding Meccan caravan routes. This provoked the Meccan tribes into sending an army to confront Muhammad’s Muslims. When word of a particularly wealthy caravan escorted by Abū Sufyān, head of the Umayyad clan, reached Muhammad, a raiding party of about 300 Muslims, to be led by Muhammad himself, was organized. By filling the wells on the caravan route near Medina with sand, the Muslims lured Abū Sufyān’s army to battle at Badr, near Medina, in March 624.
The battle proper started with an exchange of volleys of arrows, resulting in heavier casualties being suffered by the Meccan army. Muhammad gave the order to charge, throwing stones at his enemies in a traditional Arabic gesture. The Koran states that the Meccan lines broke under the force of Muhammad’s attack and speaks of angels descending from heaven to slay the fleeing enemy. A number of important Meccan leaders were among those killed, including Muhammad’s main rival, Amr ibn Hisham. The armies involved were not large: fewer than 400 Muslims and around 1,000 Meccan fighters. Despite the superior numbers of the Meccan forces (about 1,000 men), the Muslims scored a complete victory.
The victory at Badr was an important milestone in the establishment of Islam. It was even recorded in the Qurʾān as a divine sanction of the new religion: "It was not you who slew them, it was God…in order that He might test the Believers by a gracious trial from Himself" (8:17). Those Muslims who fought at Badr became known as the badrīyūn and make up one group of the Companions of the Prophet.
The victory especially raised Muhammad’s status among the Medina tribes that supported him and convinced his followers that victory over powerful and wealthy Mecca was truly possible. The victory was not destined to be swift, but by 630 Muhammad was able to march into Mecca as a conqueror.
Losses: Meccan, 100; Muslim, fewer than 20."