Constantine II in Wikipedia

Flavius Claudius Constantinus (316 – 340), commonly known as Constantine II, was Roman Emperor from 337 to 340. The eldest son of Constantine the Great and Fausta, he was born at Arles and raised as a Christian. On March 1 317, Constantine was made Caesar, and at the age of seven in 323, took part in his father's campaign against the Sarmatians. At the age of ten he became commander of Gaul, after the death of his half-brother Crispus. An inscription dating to 330 records the title of Alamannicus, so it is probable that his generals won a victory over the Alamanni. His military career continued when Constantine I chose his son field commander during the 332 campaign against the Goths. Following the death of his father in 337, Constantine II became emperor jointly with his brothers Constantius II and Constans. After the division of the empire, made by the three brothers in September of the same year in Pannonia, he ruled over Gaul, Britannia and Hispania. He was involved in the struggle between the different Christian streams. The Western portion of the empire leaned towards Catholicism and against Arianism, and Constantine freed Athanasius and allowed him to return to Alexandria. This action also put some burden on Constantius II, who was a supporter of Arianism. At first, he was the guardian of his younger brother Constans, whose portion was Italia, Africa and Illyricum. As Constans came of age, Constantine would not relinquish the guardianship and in 340 he marched against Constans in Italy, but was defeated at Aquileia and he was killed in an ambush in Cervignano del Friuli. Constans took control of his deceased brother's realm.