In 1937, the French government sent Andre' Malraux to Republican Spain to assist the elected government with aviation assets that were sent from the neutral French government. He was not a pilot nor an aeronautical engineer; he was an agent acting as an adviser on use and disposition of said assets. The Spanish Civil War lasted about 3 years; the effects are still felt throughout Spain. World War II followed almost immediately, and that history shoved the Civil War into history's closet. The country was run by the victor(s): Gen. Franco who ruled as the dictator for the next 34 years until 1974 when he died. His groomed successor immediately moved to a democratic government and shoved Franco's legacy into the garbage dump.
Historians have struggled with this topic: who won?; who lost? who were the participants? Answers are difficult to parse, and the subject matter was not made into a "hot topic". While WW II did not officially affect neutrality of Spain, it was a pass through for more than a few Allied pilots who were shot down over European fields and assisted by Spanish civilians on their trip back to England. A notable participant as a soldier was George Orwell, and he is the one writer most folks read to understand all the factions involved, including those future belligerents: Germany, Italy, and Russya(Stalin & Co.).
To read Malraux is to involve oneself in details relevant to understanding much of the politics that eventually led to war. Franco was abroad, in north Africa with his army. He could not be effective at all unless he was on the mainland. He had a logistics problem: no means of transport for his army and its needed munitions, rations, and heavy arms. Then, here comes help in the form of troop carriers that could crossover the Strait of Gibralter to deposit a trained legion of well led soldiers. The rest is history.