Constantine and the Cross is a 1961 historical drama film about the early career of the emperor Constantine, who first legalized and then adopted Christianity in the early 4th century. The fictionalised film only stretches as far into his life as the Battle of the Milvian Bridge in AD 312.
In 303 AD, Constantine became the first emperor of Gaul. Before a battle with the Romans, he has a revelation, and assures his army of the freedom of worship for all Christians. This biblical epic also shows the graphic defeat of the Roman army.
(Summary from Wikipedia)