They were created during World War II, in October 1941 as a transformation and strengthening of the assault and mountain battalions of the Milizia Volontaria per la Sicurezza Nazionale (Blackshirts) which had particularly distinguished themselves in combat.
[1] For operational use the "M" battalions were usually assigned directly to the dependencies of the Corps of the Army, with general reserve functions and from these reassigned in support of units engaged in particularly demanding actions.
On September 8, the departments deployed north of the peninsula, in France and the Balkans largely adhered to the newborn Italian Social Republic, like those landed in Corsica they partly cooperated with the fascists and the Germans.
The departments passed to the RSI were absorbed by the National Republican Army excluding the 1st Battalion "IX Settembre" which, established in September 1943 in Toulon, fought in Italy in various locations, also participating in the conflict of the landing of Anzio and on the eastern front.
The unit, equipped with armoured vehicles supplied by the Germans, was still being trained at the time of the fall of fascism (25 July 1943), renamed the 136th Armored Division "Centaur II" and purged of its most markedly fascist elements, to then be dissolved after the armistice of 8 September 1943.