In 946, he allied with Landulf II of Benevento in an invasion of Salerno with the intent of deposing Prince Gisulf I.
[1] In 955, he attempted again to throw off the imperial yoke and again an army was sent to Italy under the strategos of Calabria and Langobardia, Marianos Argyros.
In 944, Marinus was appointed co-duke, and, in that same year, Odo of Cluny visited and influenced John to affirm the possessions of the monasteries in his domains.
He and Theodora commissioned the archpriest Leo to go to Constantinople as ambassador and bring back as many Greek manuscripts as possible.
Leo returned with the Chronographia of Theophanes, the Antiquities of the Jews by Flavius Josephus, De Prodigiis by Livy, the writings of Pseudo-Dionysius the Areopagite, and the Historia Alexandri Magni.
In a vision, John saw a group of devils leading a line of horses drawing carts full of hay for the purpose of burning Pandulf Ironhead, the deceased prince of Capua, and himself, still very alive.