The Spanish Regiment of the European Brigade was initially organized as the Battalion of Spanish Legion in June 1861 as a second, but unassociated, battalion of Cazadores d’Espanola (the first was formed in May 1861 and was under the command of Major Miangoloria). Thus, for a few weeks there were two Battalions of Cazadores d’Espanola before this unit changed its name to the Battalion of Spanish Legion. The formation of the Spanish Legion did not gain traction until the first company was organized with the election of officers in July 1861. By September 1861 the Battalion of Spanish Legion, now with three companies, was formed under the command of Major P. Avendano (previous Captain of Spanish Legion Co. A). A fourth company was added to the battalion in mid-October 1861. State records, however, have the first four companies of the Spanish Legion as being unattached and subordinate to the First Division of Louisiana Volunteer Troops in November 1861, suggesting the battalion was formed later. Given the multiple press reporting throughout the Summer of 1861, it is highly likely that the battalion did exist prior to November 1861 and State records were inaccurate. In late-1861 or early-1862 the Battalion of Spanish Legion was expanded to a regiment under the command of now Col. P. Avendano. As a result of the 23 January 1862 Militia Act, the Spanish Legion Regiment was subordinated to the European Brigade which formally organized on 22 February 1862. In early-March 1862, elements of the Spanish Rifle Regiment (Cazadores de Espanoles) to include its Colonel, Puig, joined this regiment and the Spanish Legion Regiment’s named was changed to the "Spanish Regiment". At times it was designated the 3rd, 4th and later the 5th regiment of the European Brigade.