The National Republican Army was officially formed on 28 October 1943 by merging the former Royal Italian Army (Regio Esercito) units that were still loyal to fascist dictator Benito Mussolini and Italian pro-fascist units raised by the Germans after the occupation of Southern Italy.

By the end of the war, the National Republican Army collapsed due to the Allied offensive along with the general insurrection by the Italian partisans in northern Italy.

The RSI became so desperate for soldiers that it granted freedom to prisoners if they would join the army, and the death penalty was imposed on anyone who resisted conscription.

[2] Autonomous military forces in the RSI also fought against the Allies, including the Decima Flottiglia MAS commanded by Prince Junio Valerio Borghese (National Republican Navy).

However, possibly because of the Allies' low opinion and regard for the Italian Social Republic, Graziani's signature was not required at Caserta.

The majority of deaths, around 21,600, were caused by anti-party formations, such as National Republican Guard, Black Brigades, and Territorial Defense Militia.

[6] Following Italy's withdrawal from the Axis alliance on 8 September 1943, the Wehrmacht disarmed and captured Italian soldiers as part of Operation Achse, deporting some 650,000 to the German Reich and occupied territories.

[7] A small percentage of these internees, along with volunteers and conscripts from Italy, were sent to southern Germany, mainly to military camps in Heuberg, Münsingen, Grafenwöhr and Sennelager, where they were raised, trained and equipped to form the National Republican Army.

[9] The National Republican Army comprised the following four divisions: There were also a large number of smaller autonomous units.