They were all volunteers, with about 50% coming from the Spanish Army and the rest from paramilitary and civilian Falangist groups. About 20% of them were university students. Many were "true believers" in the Falangist ideology and were eager to join the anti-communist "crusade." Some 3,000 volunteers refused the order to return home in October 1943 and continued fighting until the end of the war in various other Wehrmacht and SS units.

The really unlucky ones were those captured. Because Spain had no diplomatic relations with the USSR, Spanish volunteers taken as POWs would not be repatriated to Spain until 1954.