The Legion was created by a royal decree of January 28, 1920, | Forteresse Europe

The Legion was created by a royal decree of January 28, 1920, signed by the Minister of War, Don José Villalba Riquelme. It then bore the name of the battalion of foreigners. The purpose of this creation was to face the difficulty of the fighting of the Rif war in Morocco; Spanish authorities thought then, as France had done before, that it was the only solution to compensate for the failings of an army of conscripts ill-prepared for these confrontations.

The first commander of the Legion was Lieutenant-Colonel José Millán-Astray. It was he who gave it its particular style and this "idealistic" aspect. This unit allowed foreigners wishing to fight voluntarily in Morocco to join the Spanish army.

The chosen creation date of the Legion is not that of the decree, but usually that of the engagement of the first legionary, September 20, 1920.