 It was important to many Spaniards to eliminate vestiges of this history by converting Spain's long-standing bilateral relations with the United States into a multilateral undertaking through NATO.The outcome of the 1986 referendum on membership in NATO committed the Spanish government to negotiate the reduction of the United States military presence in Spain.Spain insisted that the F-16 aircraft be removed from Torrejón as a condition for renewal of the base agreement, and the Spanish government threatened to expel all United States forces in Spain if this demand were not accepted.