Including parts of France. They went up against Christians who happened to not be Roman. They also sacked Constantinople, which was Christian but not Roman.
Constantinople New Rome was the capitol of the Empire of Romania, inhabitated by a people who called themselves Romans, who spoke the Roman language of Greek, and who were called by their enemies the Turks and Arabs as Romans, and ruled over by a man styled the Roman Emperor who traced his ruling authority straight back to Heraclius, Justinian, Constantine, Augustus and Caesar. How were they not Romans?
When the Turks conquered this area they called it the Sultanate of Roum (Rome) - Anatolia, and the Sultanate of Roumelia (Little Rome) - Balkan Peninsula.
Time for some history education.
http://www.romanity.org/htm/frame_friesian_en.htm
http://www.romanity.org/index.htm