Writes Justo L. González in the second volume of his “The Story of Christianity”:

One of the main issues confronted by all Christians in the twenty-first century is how to live in the post-Constantinian era. What is meant by this phrase is that the church can no longer count on the political support that it enjoyed since the times of Constantine. As we have seen in the preceding chapters, in a process beginning with the American and French Revolutions, Western Christianity had to face the challenge of secular states that, although not always hostile, tended to ignore it. For Eastern Christianity, on the other hand, that process began when Constantinople fell to the Turks in 1453.

(p. 373)