Nicene and Post-Nicene Fathers, Ser. II, Vol I:
The Life of Constantine with Orations of Constantine and Eusebius.: Chapter XXVI

Chapter XXVI.—How he resolved to deliver Rome from Maxentius.

While, therefore, he regarded the entire world as one immense body, and perceived that the head of it all, the royal city of the Roman empire, was bowed down by the weight of a tyrannous oppression; at first he had left the task of liberation to those who governed the other divisions of the empire, as being his superiors in point of age. But when none of these proved able to afford relief, and those who had attempted it had experienced a disastrous termination of their enterprise, 3103 he said that life was without enjoyment to him as long as he saw the imperial city thus afflicted, and prepared himself for the overthrowal of the tyranny.

Footnotes

Referring to the unsuccessful expeditions of Severus and Galerius.