History of the Roman Empire from this point on, leading his biographers to label him as insane. Most of what history remembers of Caligula comes from Suetonius, in his book "Lives of the Twelve Caesars". According to Suetonius, Caligula once planned to appoint his favourite horse Incitatus to the Roman Senate. He ordered his soldiers to invade Britain to fight the Sea God Neptune, but changed his mind at the last minute and had them pick sea shells on the northern end of France instead. It is believed he carried on incestuous relations with his three sisters: Julia Livilla, Drusilla and Agrippina the Younger. He
Holy Roman Emperor with very few exceptions, taken on a role as promoters and defenders of Christianity . The title of "Emperor" became defunct in Western Europe after the death of Julius Nepos in AD 480, although the rulers of the barbarian kingdoms continued to recognize the Eastern Emperor at least nominally well into the 6th century; both the title and connection between Emperor and Church continued in the Eastern Roman Empire until 1453, when it fell to the forces of the Ottoman Empire. In the west, the title of Emperor ("") was revived in 800, which also renewed ideas of imperial–papal cooperation.