The Guardia alla Frontiera (GaF) (transl. Border Guard), was an Regio Esercito Border guard created in 1937^[1] who defended the 1,851 km of northern Italian frontiers with the so-called "Vallo Alpino Occidentale" (487 km with France), "Vallo Alpino Settentrionale" (724 km with Switzerland and 420 km with Austria) and "Vallo Alpino Orientale" (220 km with Yugoslavia).

In 1940 the GaF had 21,000 military personnel, deployed in eight commands, 27 sectors and seven regiments of artillery. It manned 1,000 fortifications, 6,000 machine guns, 1,000 mortars, 100 Cannone da 47/32 M35 , and another thousand other medium and small-caliber cannons (75/27 and 149/35).

By 10 June 1940 (Italy's entry into the war) the GaF (not counting colonies in Libya and Albania) contained 23 sectors, 50,000 men, 28 battalions "Vallo Alpino", and 22 battalions of fascist militia.

Each command of the army of GaF could be divided into "sectors" (27 areas of coverage, from I to XXVII, along the border; sectors XVIII, XIX and XX were never realized), which could be broken down into subsectors and so on for ever smaller units. Each command in the field had two or more subsectors which controlled the fortifications. These works were manned by infantry, artillery, engineers, etc. Despite the GaF being predominantly static it also received five light tank (carristi) companies, equipped with Fiat 3000 tanks that over time, due to their age and lack of spare parts, ended largely abandoned in Sector armories or buried to use the turrets as a fort.

The Guardia alla Frontiera disappeared after 1943, but nominally was active until 1953.^[2]