Battle of Mons Seleucus

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Battle of Mons Seleucus
Part of the Roman civil war of 350–353
Date3 July 353
Result Decisive Constantius victory
Roman Empire Roman Empire
Commanders and leaders
Constantius II Magnentius

The Battle of Mons Seleucus was fought in 353 between the forces of the legitimate Roman emperor Constantius II and the forces of the usurper Magnentius. Constantius' forces were victorious, and Magnentius later committed suicide.

It took place in La Bâtie-Montsaléon in today's department Hautes-Alpes, Southern France.


After defeat at the battle of Mursa Major in September 351, the rebel Magnentius attempted to reestablish his defense along the eastern Alps, basing himself at Aquileia.[1] However, he alienated all of Italy by his cruel massacres after the suppression of the Flavianist upstart Nepotian, and the revolt of the province in his rear forced his further retreat; the pursuit of Constantius II.' generals, who had surprised the passages of the Alps, was checked at Pavia, and Magnentius retired in safety to Gaul.[2]

The dilatory Constantius, determined to decide the contest by overwhelming might rather than by activity and speed, stirred the Franks and Alemans across the Rhine to invade the dominions of the usurper in Gaul, meantime despatching contingents to conquer Spain and Africa.[3] Only when the Imperial fleet had entered the Rhone to capture Lyons in Magnentius' rear, and news arrived that his brother Decentius was besieged in Sens by the Alemans under Chnodomarius,[4] while northern Gaul had abandoned his allegiance, did Constantius bestir himself against the usurper.[5]

The armies met at Mons Seleucus in the modern department of Hautes-Alpes near Gap, in south-eastern France. Constantius, after a bloody day, was again victorious, and Magnentius, deserted by his house-hold guard, took his own life.[6]


Constantius II became the undisputed Emperor of the Roman Empire; the former adherents of Magnentius were cruelly persecuted,[7] and Constantius' attentions were freed against the Nicene Church under Athanasius, Primate of Alexandria, who besides opposing the emperor's theological opinions, had supposedly given a favorable reception to the ambassadors of the usurper.[8] The Synods of Arles and Milan, in that and the succeeding years, subscribed the impeachment of the haughty bishop, and with the ratification of the later synods of Rimini and Seleucia, the entire Roman world was for a brief while Arian.[9] Coordinates: 44°27′35.3″N 5°44′10.5″E / 44.459806°N 5.736250°E / 44.459806; 5.736250


  1. ^ Edward Gibbon, The Decline and Fall of the Roman Empire, (The Modern Library, 1932), ch. XVIII., p. 595
  2. ^ Gibbon, p. 596
  3. ^ Gibbon, Ibid.
  4. ^ Gibbon, chap. XIX., pp. 622, 626
  5. ^ Gibbon, ch. XVII pp. 596, 597
  6. ^ Gibbon, Ibid.
  7. ^ Gibbon, pp. 597, 598
  8. ^ Gibbon, chap. XXI., pp. 705-7
  9. ^ Gibbon, p. 697