Final answer:
Constantine changed the religious policy of the Roman Empire by issuing the Edict of Milan in 313, which allowed for religious toleration and made Christianity a legal religion. This action paved the way for Christianity to become the dominant faith in the empire, though it did not become the official religion until later.
Step-by-step explanation:
How Constantine Changed the Religious Policy of the Roman Empire
Emperor Constantine significantly altered the religious landscape of the Roman Empire through a series of decisive actions. His reign marked a turning point for Christianity, which began a transition to becoming the dominant religion within the empire. The Edict of Milan in 313 was one such action, which proclaimed religious toleration throughout the empire and effectively made Christianity a legal religion. This edict ended the state-sponsored persecution of Christians and allowed citizens to worship any deity they wished. However, it is crucial to note that Christianity was not made the official religion of the Roman Empire during Constantine's rule; that occurred later in the 4th century under Emperor Theodosius. The acceptance and support of Christianity by Constantine greatly increased its influence and aligned the church closer to the mechanisms of imperial power, thus dramatically changing the religious policies that had long favored Roman polytheism.