How did Constantine I defeat Maxentius at the Battle of Milvian Bridge?

Constantine I defeated Maxentius at the Battle of the Milvian Bridge on October 28, 312 CE, during a lightning campaign in the Roman Empire.12

Prior to the engagement, Maxentius had cut the Milvian Bridge and other crossings over the Tiber River to impede Constantine’s advance toward Rome. However, Maxentius ultimately chose to confront Constantine’s forces on the far side of the river, utilizing a temporary pontoon bridge he had constructed.2

During the ensuing battle, Constantine’s army broke the forces of Maxentius. In the resulting chaos, the retreating troops attempted to flee back across the Tiber, but the pontoon bridge became overloaded and collapsed. Many soldiers, including Maxentius himself, fell into the river and drowned.2

Ancient sources, such as Lactantius and Eusebius of Caesarea, attribute Constantine's success to divine intervention. They report that Constantine experienced a vision or dream of a Christian symbol—the cross or the Chi-Rho—leading him to mark his soldiers' shields or carry the labarum into battle.2