During World War I, the Italian Army employed thousands of foreign volunteers. The reluctance of the military command to deploy these volunteers was heightened by the legal difficulties of arming Austro-Hungarian citizens who had been captured during the conflict. The government only approved the creation of Czechoslovak, Polish, and Romanian volunteer units in the spring of 1918, pushed by the Supreme Command and officers, often from "irredentist" Trentino or Giulian regions, who believed that enlisting former Austro-Hungarian prisoners willing to fight against the Dual Monarchy would aid the war effort and serve propaganda purposes. 

Initially, small "contact" units were formed to engage with enemy soldiers of the same nationality in an attempt to weaken their morale, extract information, and encourage desertion. By 1917, small companies of Romanians, Poles, and especially Czechoslovaks were created. In April 1918, the 6th Division, also known as the Czechoslovak Legion, was formed. It consisted of about 10,000 men, with some Italian officers and specialists. The division was structured into two brigades, each with two regiments of three battalions, along with two additional battalions and support services. 

On May 24, war flags were presented to the division on the Capitoline Hill in Rome. The 1st Battalion of the 33rd Regiment was deployed in mid-June on the Piave River. The division was later assigned to the Trentino front, in the area of Monte Baldo, where it remained until the end of the war under the command of General Andrea Graziani. On the eve of the armistice, the division was expanded into a corps, with additional cavalry squadrons, two armored cars, and an SVA aircraft. 

On December 8, in Padua, the legionaries swore allegiance to the newly-formed Czechoslovak Republic before being repatriated. Other Czechoslovak prisoners of war were organized into over 50 territorial battalions, which returned to Czechoslovakia throughout 1919. A group of Italian officers accompanied the Czechoslovak corps to Prague, where the corps was soon engaged in combat against the Hungarians.