John Firth 
Constantine the Great [EPUB ebook] 

THE catastrophe of the fall of Rome, with all that its fall signified to the fifth century, came very near to accomplishment in the third. There was a long period when it seemed as though nothing could save the Empire. Her prestige sank to the vanishing point. Her armies had forgotten what it was to win a victory over a foreign enemy. Her Emperors were worthless and incapable. On every side the frontiers were being pierced and the barriers were giving way…