Complex sentence: Early Christian writers (e.g. Eusebius) frequently identified Gog and Magog with the Romans and their emperor, but after the Empire became Christian this was no longer possible, and attention switched to Rome's northern barbarian enemies.
Split into simpler sentences: Early Christian writers (e.g. Eusebius) frequently identified Gog and Magog with the Romans and their emperor. After the Empire became Christian this was no longer possible, and attention switched to Rome's northern barbarian enemies.