The XII International Brigade was mustered on 7th November 1936 at Albacete, Spain. It was formally named the Garibaldi Brigade, after the Italian partisan leader, Giuseppe Garibaldi. Its first commanding officer was a soviet advisor of Hungarian origin, Gen. "Pavol Lukács" (Mate Zalka), who went on to command the 45th Division of the Spanish Republican Army. (He was killed during the Huesca Offensive.)
The brigade included, among others, the following battalions: