The Battle of Frigidus took place in 394 AD between the forces of the Roman Emperor Theodosius I and the usurper Eugenius. This battle was significant as it marked the last major conflict of the Roman Empire's civil wars. Theodosius aimed to restore unity in the empire and eliminate the threat posed by Eugenius, who had gained support from various factions. The battle occurred near the Frigidus River in modern-day Slovenia. Theodosius's army, bolstered by the support of the Visigoths, ultimately defeated Eugenius's forces. This victory solidified Theodosius's power and helped establish Christianity as the dominant religion in the Roman Empire.