The Battle of the Frigidus took place in September 394 AD between the forces of the Roman Emperor Theodosius I and the usurper Eugenius. This conflict occurred near the river Frigidus in present-day Slovenia. Theodosius aimed to restore unity to the Roman Empire, which had been divided between different rulers. The battle was marked by harsh weather conditions, including heavy rain and snow, which affected the troops' morale and effectiveness. Ultimately, Theodosius emerged victorious, leading to the defeat of Eugenius and the consolidation of his power over the Roman Empire. This battle was significant in shaping the future of the empire.