The Voluntary Militia for National Security was an autonomous armed force of the Kingdom of Italy with which Benito Mussolini merged the Action Squads of the National Fascist Party and was none other than the party's paramilitary organization.

Commonly referred to as "black shirts" due to the color of the uniform, the militiamen swore to the Head of Government and not to the Sovereign and over time they became a real armed force alongside the Royal Army with which they were initially in open contrast.

The departments of the Voluntary Militia had an organization based on the Roman model both for the definition of armed groups, which were divided into maniples, centuries, cohorts and legions, and for the identification of ranks (leader, centurion, consul).

As stated in the Royal Decree which recognized its institution, the Militia for National Security was at the service of God and the Fatherland and under the orders of the Head of Government. It provided, in competition with the armed corps for Public Security and with the Royal Army, to maintain public order within and prepared and kept the citizens framed for the defense of Italy's interests in the world.

The recruitment was voluntary and took place among members of the fascist militia who applied for it aged between 17 and 50 years and who, in the opinion of the Prime Minister or the authorities delegated by him, possessed the requisites of capacity and morality required.