Constantine the Great is a titanic figure in Roman, and indeed world history. Most famed for making Christianity the official religion of the Roman Empire (and thus ensuring its survival and spread), and for moving the seat of imperial rule to 'New Rome' (Constantinople), he is most often studied for his religious and political impact. But it is often forgotten that his power and success was made possible by the use of armed force, in an impressive military career which is well worthy of study in its own right. Constantine won victories over external barbarian armies as well as defeating the Roman armies of his internal rivals in civil war.