Constantine II ( emperor ) Constantine II ( ) ( January / February 316 – 340 ) was Roman Emperor from 337 to 340 . Son of Constantine the Great and co - emperor alongside his brothers , his attempt to exert his perceived rights of primogeniture led to his death in a failed invasion of Italy in 340 . Career . The eldest son of Constantine the Great and Fausta , after the death of his half - brother Crispus , Constantine II was born in Arles in February 316 and raised as a Christian . On 1 March 317 , he was made Caesar ; at the age of seven , in 323 , he took part in his father ' s campaign against the Sarmatia ns . At age ten he became commander of Gaul , following the death of 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 made him field commander during the 332 campaign against the Goths . Following the death of his father in 337 , Constantine II initially became emperor jointly with his brothers Constantius II and Constans , with the Empire divided between them and their cousins , the " Caesars " Dalmatius and Hannibalianus . This arrangement barely survived Constantine I ’ s death , as his sons arranged the slaughter of most of the rest of the family by the army . As a result , the three brothers gathered together in Pannonia and there , on 9 September 337 , divided the Roman world between themselves . Constantine , proclaimed " Augustus " by the troops received Gaul , Britannia and Hispania . He was soon involved in the struggle between factions rupturing the unity of the Christian Church . The Western portion of the Empire , under the influence of the Popes in Rome , favored Catholicism over Arianism , and through their intercession they convinced Constantine to free Athanasius , allowing him to return to Alexandria . This action aggravated Constantius II , who was a committed supporter of Arianism . Constantine was initially the guardian of his younger brother Constans , whose portion of the empire was Italia , Africa and Illyricum . Constantine soon complained that he had not received the amount of territory that was his due as the eldest son . Annoyed that Constans had received Thrace and Macedonia after the death of Dalmatius , Constantine demanded that Constans hand over the African provinces , to which he agreed in order to maintain a fragile peace . Soon , however , they began quarreling over which parts of the African provinces belonged to Carthage , and thus Constantine , and which belonged to Italy , and therefore Constans . Further complications arose when Constans came of age and Constantine , who had grown accustomed to dominating his younger brother , would not relinquish the guardianship . In 340 Constantine marched into Italy at the head of his troops . Constans , at that time in Dacia , detached and sent a select and disciplined body of his Illyrian troops , stating that he would follow them in person with the remainder of his forces . Constantine was engaged in military operations and was killed in an ambush outside Aquileia . Constans took control of his deceased brother ' s realm .