This is a new and provocative study reevaluating the history of the struggle between orthodoxy and heresy in the early church. Professor Williams argues that the traditional picture of Nicene ascendancy in the western church from 350 to 381 is substantially misleading, particularly that the conventional portrait of Ambrose of Milan as one who rapidly and easily overpowered his Arian opponents is a fictional product derived from idealized accounts of the fifth century. Sources illustrating the struggle between orthodox pro-Nicenes and 'Arians', or Homoians, in the fourth century reveal that Latin Arianism was not the lifeless and theologically alien system that historians of the last century would have us believe. Professor Williams shows that the majority of churches in the west had little practical use for the Nicene Creed until the end of the 350s - over twenty five years after it was first issued under Constantine - and that the ultimate triumph of the Nicene faith was not as inevitable as it has been assumed. Ambrose himself was seriously harassed by sustained attacks from the Homoians in Milan for the first decade of his episcopate, and his early career demonstrates the severity of the religious conflict which embroiled the western churches, especially in North Italy. Only after an intense and uncertain decade did Ambrose finally prevail in Milan once the Nicene form of faith was embraced by the Roman Empire and Arianism was outlawed as heresy. This is an innovative and challenging book, full of illuminating new insights on the social, political, and theological entanglements of the early church.