The first Italian intelligence organization was established in the early 1900s to gather and analyse information mainly for military purposes, when the Ufficio I [1st Office] was set up within the Army Staff to support the High Command with intelligence.
 
After WW1,  the need was felt to organize intelligence in a more effective way by differentiating  military from civilian intelligence. During a lengthy process, besides military intelligence branches – some of them operating abroad – units were set up within the Ministry of the Interior with the task to develop intelligence in Italy.

As early as in 1919, intelligence was reorganized within the Ministry of the Interior. The  Divisione affari generali e riservati (DAGR) [General and Confidential Affairs Division] was established  upon the dismantling of the Ufficio centrale di investigazione (UCI) [Central Investigation Office] – created during WW1 to find deserters and their supporters.

The DAGR had two different units: the Sezione ordine pubblico [Public Order Section], entrusted with protecting of the State’s security and countering subversive activities – and the Divisione Stranieri [Foreigners Division] – tasked with gathering information on foreigners in Italy. In May 1925, a new unit was set up within the DAGR – the Ufficio Speciale Movimento Sovversivo [Special Subversive Movement Office] – to control and suppress subversive activities.

In those years, espionage techniques were developed and enhanced, and the Casellario Politico Centrale [Central Political Records Information System] and the Ispettorati Speciali di Polizia [Special Police Inspectorates] were set up in many Italian regions.

As to military intelligence,  Royal Decree no. 70 of 6 February 1927 reorganized the Army Staff Command and established the Servizio Informazioni Militare (SIM) [Military Intelligence Service] directly answerable to the Chief of Staff.

The SIM had two branches: the offensive unit focusing on intelligence, and the defensive unit specializing in counterespionage. This organizational structure remained unchanged until 8 September 1943, except for a short period when the SIM's defensive unit was organized as an autonomous counterespionage service. Similar services were set up for the Navy and Air Force.

In 1944, after the first phase of the reform of public security by the Government, the Servizio Informazioni Speciali (SIS) [Special Intelligence Service] was established and provisionally entrusted with political investigations for which the DAGR had been responsible for in the past.

The SIS operated for about four years. In late 1948, it was replaced by the Ufficio Affari Riservati  [Confidencial Affairs Office] of the Ministry of the Interior.

After WW2, on the other hand, the SIM  was reorganized within the General Staff. When the Ministry of Defence replaced the Ministries of War, Navy and Air Force, on 30 March 1949 the reorganization of the three armed forces was completed and a single central service was established – the Servizio Informazioni Forze Armate (SIFAR) [Armed Forces Intelligence Service], directly answerable to the Defence Chief of Staff.

At the same time, a Sezione Informazioni Operative e Situazione (SIOS) [Operations and Situation Intelligence Section] was established within each armed force – directly answerable to its respective Chief of Staff and entrusted with technical and military intelligence as well as military police tasks. The SIOS units cooperated and liaised with the SIFAR.

The SIFAR underwent a gradual development based on the internal provisions of the Defence Chief of Staff until Decree of the President of the Republic no. 1477 dated 18 November 1965 – regarding the organization of Defence Staff and the Staffs of the Army, Navy and Air Force – established the Servizio Informazioni Difesa (SID) [Defence Intelligence Service], under the authority of the Defence Chief of Staff. The SID was entrusted with intelligence, prevention, protection of military secrets and any other matter involving national security and the defence of the State.

Law no. 801 of 1977 organically reformed the sector and established the Servizio per le informazioni e la sicurezza militare (SISMI) [Military Intelligence and Security Service] and the Servizio per le informazioni e la sicurezza democratica (SISDE) [Intelligence and Democratic Security Service]. The two services remained under the authority of the Ministry of Defence and the Interior respectively, but the law vested the President of the Council of Ministers with the oversight of, the overall political responsibility for and coordination of security intelligence policy. The President of the Council of Ministers coordinated the two intelligence services through the CESIS (Comitato Esecutivo per i servizi di informazione e sicurezza) [Executive Committee for information and security services].

Law no. 124 of 2007 reformed the entire Italian intelligence community establishing the Sistema di informazione per la sicurezza della Repubblica [Intelligence System for the Security of the Republic]. Under this System, the oversight and the overall responsibility are vested in the President of the Council of Ministers, coordination is entrusted to the Dipartimento informazioni per la sicurezza (DIS) [Security Intelligence Department], while the Agenzia informazioni e sicurezza esterna (AISE) [External Intelligence and Security Agency] and the Agenzia informazioni e sicurezza interna (AISI) [Internal Intelligence and Security Agency] are no longer under the authority of the Ministers of Defence and of the Interior.

The AISE replaced the SISMI and became a civilian intelligence service. It is tasked with intelligence activities against external threats, counterespionage outside the national territory and counterproliferation.

The AISI replaced the SISDE and is entrusted with intelligence activities for the defence of the internal security of the Republic and its democratic institutions, as well as the protection of national interests and counterespionage in Italy.