On December 11, 1941, Cuba and the United States of America, Costa Rica, The Dominican Republic, Guatemala and Nicaragua declare war on Nazi Germany and Fascist Italy.

[3] On January 14, 1942, the Cuban Secretary of State (José Manuel Cortina) indicates in a diplomatic message to the American Chargé in Cuba (Ellis O. Briggs) the following "I take pleasure in advising you that the Government of Cuba, inspired by the lofty sentiments of cooperation and alliance which joins the Cuban Nation with the United States of America in the present war, engaged in the territorial defense of America and of every one of the American nations, as well as of the principles of democracy and of the liberty of the peoples, has accepted the suggestions of your Government which were transmitted by the Embassy in the above-mentioned notes."

The above-mentioned notes were two and included 5 specific points of suggestion including in part: Stationing of US Aviation Corps Detachments in certain airfields (i.e. La Fé, in the Province of Pinar del Río; Rancho Boyeros, in the Province of Habana; and in Camagüey); Permission to use Cuban landing fields; Permission to take photographs of Cuban territory for aerial navigation charts, etc.

June 26, the United States established Naval Air Auxiliary Station (NAAS) (Lighter-than-Air), San Julián, Cuba.

NAAS San Julián was established on the western tip of Cuba near Pan American World Airways' Isabel Rubio Emergency Landing Field.

The Pinar del Río area was considered ideally situated for further development and the Army began construction by expanding the existing Pan American airfield on November 1.

January 1, the United States Army Air Forces (USAAF) set up postal operations for San Julián using a non-descript number.

[11] October 1, the US Navy's Bombing Squadron One Hundred Twenty Five (VB-125) sent a three-aircraft detachment to NAF San Julián for ASW patrols.

The squadron was under the operational control of Fleet Airship Wing Twelve (FAW-12) and stayed in San Julián until February 11, 1945 when they we relieved by VPB-145.

[15] February 8, by means of Decree 409, the control of civil aviation is transferred from the Cuban Army to the newly created Commission of National Transportation.

Early preparations for the invasion included the Cuban Democratic Revolutionary Front (FRD) on October 26, 1960 distributing its first Combat Order.