was Bishop Arnulf of Metz), yet had never been used by a reigning king and was thus appropriate for an illegitimate eldest son. The choice of the name is the surest evidence that Liutswind and Carloman were not legally married. Around 860, Arnulf and his cousin, Hugh, the illegitimate son of Carloman's brother Louis, were both in Koblenz at the court of their grandfather, who was probably overseeing their military education and also holding them to ensure the good behaviour of their fathers. Guardian of the southeastern frontiers In 856, Louis first associated Carloman with his rule by appointing him governor of Carantania. According to the Annales Fuldenses (863), he was given the title "prelate of the Carantanians" (). Since this was his first governorship, Louis did not give him rule over the entire March of Pannonia, with traditional seat of frontier governor (prefect) at Tulln. Instead, Carloman was given rule over the inner region (Carantania), in order do gain experience, and perhaps because his father wanted to keep him from trying to seize too much power. Gaining the first foothold of power in Carantania, Carloman moved to assume a more prominent role in governorship over the frontier regions of his father's realm. Starting from 857, Carloman was occasional witnesses to his father's charters, and already in 858 he was appointed to lead a military expedition against the Great Moravia. In 861, Carloman came into conflict with several frontier commanders in southeastern regions, expelled them from their offices, and replaced them with his loyals. That move was made without his fathers consent, and by 862 an open conflict erupted, with Carloman siding with Rastislav of Moravia and taking control over all southeastern regions, advancing further into Bavaria, up to the river Inn. An attempted reconciliation and truce between father and son failed, and in 863 king Louis invaded his sons territory, forced Carloman into submission, and took him into custody. Replaced by count Gundachar, who was appointed governor of eastern marches by king Louis (863), prince Carloman remained in his father custody until 864, when he escaped and returned to Carantania. Welcomed by supporters, he assumed power in the province. At that time, king Louis was campaigning against Moravia, but ceased further operations and moved south, towards Carantania. Conflict was avoided by reconciliation. Father and son met and reached an agreement. Carloman submitted to his father and in return he