Library Eusebius of Caesarea Life of Constantine
Book 1, Chapter 37: Defeat of Maxentius's Armies in Italy.
Constantine, however, filled with compassion on account of all these miseries, began to arm himself with all warlike preparation against the tyranny. Assuming therefore the Supreme God as his patron, and invoking His Christ to be his preserver and aid, and setting the victorious trophy, the salutary symbol, in front of his soldiers and bodyguard, he marched with his whole forces, trying to obtain again for the Romans the freedom they had inherited from their ancestors.
And whereas, Maxentius, trusting more in his magic arts than in the affection of his subjects, dared not even advance outside the city gates, but had guarded every place and district and city subject to his tyranny, with large bodies of soldiers, the emperor, confiding in the help of God, advanced against the first and second and third divisions of the tyrant's forces, defeated them all with ease at the first assault, and made his way into the very interior of Italy.
English translation by Ernest Cushing Richardson, in Nicene and Post-Nicene Fathers, Series II, Vol. I (eds. Philip Schaff and Henry Wace; Buffalo: Christian Literature Publishing Co., 1890). Public domain. Digital text via New Advent Church Fathers.