Constantine became the first Christian emperor. What incident led to his conversion to Christianity

A vision of a Christian symbol promised him victory during a crucial battle.

Explanation:

According to Christian historians of late antiquity, Constantine saw a Christogram, an early Christian symbol, in the sky the morning before the battle of the Milvian bridge on 28 October 312 AD, whose victory Constantine attributed to the influence of the Christian god. Due to that vision, Constantine used the Christogram, the sign of the Cross, as a banner against his enemies during the battle. In fact, because of his victory, Constantine adopted the phrase In hoc Signo Vinces, which in Latin means "In this sign thou shalt conquer." This event marked the beginning of the conversion of Constantine to Christianity. For that victory, Constantine became emperor of the Roman Empire and he was the first emperor in legalizing Christianity in the Roman Empire.

a vision of a christian symbol promised him victory during a crucial battle