The Italian Legion was established on 27 October 1936, through an agreement signed in Paris between Italian republicans, socialists and Communists. It was headed by the Republican commander Randolfo Pacciardi and Communist political commissars Antonio Roasio, Luigi Longo and socialist Amedeo Azzi. It was part of the XII International Brigade along with André Marty Battalion and Dimitrov Battalion. It had a baptism of fire on the November 13, 1936 at Cerro de los Ángeles during the Siege of Madrid, then the battalion fought by the University of Madrid, at Pozuelo, Boadilla del Monte, Mirabueno, Majadahonda and Jarama. During the Battle of Jarama, Pacciardi was wounded, and so Ilio Barontini took command of the battalion during the Battle of Guadalajara. Pacciardi was again the commander at Huesca and Villanueva del Pardillo.