October 28, 312

The Battle of the Milvian Bridge and Constantine's Vision

In 312 Constantine crossed the Alps and marched on Rome. At the Milvian Bridge he defeated Maxentius's army. Maxentius drowned in the Tiber, and Constantine became master of the entire West.

According to Lactantius, Constantine received instructions in a dream to place the monogram of Christ (chi-rho) on his soldiers' shields. According to Eusebius, he saw a cross in the sky with the words "by this conquer".

The two accounts differ. Scholars debate the sincerity and depth of his conversion. They note that Constantine continued for some time to honor the cult of the Unconquered Sun.