Fighting opened, as tradition records it, with single combat between champions: Hamza ibn Abd al-Muttalib, Ali ibn Abi Talib and Ubaydah ibn al-Harith met three Meccan nobles before the main lines engaged. In the general fighting that followed, the smaller Muslim force broke the Quraysh line. Among the Meccan dead was Abu Jahl, the expedition's leading commander and one of Muhammad's most prominent opponents at Mecca, along with several other senior Quraysh figures; the Quran's account of the battle, in Surah al-Anfal, frames the outcome as aid sent to a force that had gone into the field heavily outnumbered. A number of Quraysh were taken prisoner and later ransomed or freed.
The immediate military stakes at Badr were modest measured against the size of either city, but the political consequences were not. The defeat cost Mecca several of its most senior men and, for the first time, demonstrated that the Muslim community at Medina could defeat a Meccan force in open battle. For Muhammad, the victory strengthened his authority within Medina and hardened the conflict with Mecca, which sought a measure of revenge the following year at Uhud. Modern historians treat the numbers on both sides, drawn from tradition rather than an independent record, with some caution, though the broad shape of the encounter, a small Muslim raiding party and a larger Meccan relief force, is not contested.