The first formation of the Co-belligerent Army was the I Motorized Grouping (Italian: I Raggruppamento Motorizzato) created on 27 November 1943 in San Pietro Vernotico near Brindisi.

[2] Some of the soldiers who joined the unit had managed to evade capture and internment by German forces.

The unit was commanded by General Vincenzo Dapino, who led it during its first engagement in the Battle of San Pietro Infine in December of the same year.

In early 1944, a 5,000-man force of Italians fought on the Gustav Line around Monte Cassino and acquitted itself well.

On 24 September 1944, the CIL was disbanded and its personnel and units used to form the first combat groups: "Legnano" and "Folgore".

The Combat Groups were given the names of old Royal Army divisions and followed the numbering system of older regiments to some extent.

[9] Not directly dependent from the Allied Headquarters in Italy the Co-Belligerent Army also deployed three Internal Security Divisions (Divisioni di Sicurezza Interna) for internal security duties: In 1946, the Kingdom of Italy became the Italian Republic.

[11] Some sources estimate the overall number of members of the Italian regular forces killed on the Allied side as 5,927.