The 'Battle of Mardia', also known as 'Battle of Campus Ardiensis', was fought in late
316/early
317 between the forces of
Roman Emperors
Constantine I and
Licinius. Constantine won the battle, and, according to a peace signed on
1 March 317, Licinius ceded territory to him, and had to execute
Valerius Valens, whom Licinius had appointed
Caesar before the battle. The peace lasted for about seven years.
References
★
Valens article at DIR