Axis Spain
My view has always been that Spain, along with Ireland, would only join the Axis Allinace once Britain is out of the war. Now, I'm not suggesting some aquatically mammalian happening but the oft-repeated idea of Halifax becoming Prime Minister on 13 May 1940 and suing for peace through Italy or Sweden two weeks later once the scale of the German victory had become clear.
Suppose then that happens - I'm not suggsting at this point that Gibraltar would be handed to Spain any more than Malta would go to Italy or Ulster to Eire. It's not in Berlin's interests to make that kind of peace.
Presumably, the Spanish would then want to make a more significant contribution to the fight against Bolshevism in 1941.
What then ? Well, anything could have happened but let's assume events flow as in OTL and Barbarossa begins on June 22nd 1941. My thought has always been that IF Japan attacks Pearl Harbour on schedule AND the German offensive falters in front of Moscow, Halifax would tear up the Peace Treaty of 1940 and declare war on the Axis in early 1942.
The Spanish might well blockade Gibraltar but there's nothing of any value left by then - the North Africa campaign runs to early 1944 (it started later than in OTL) by which time American and British forces have broken the Afrika Korps.
Do the allies land in Spain ? No, bacause the Pyrenees represent a defensive line and the more direct routes to Berlin lie through Italy, the Adriatic and Northern France.
D-Day, the landing in southern France, is on August 11th 1944 and American, British and Empire forces soon cut German troops off in SW France and Spain. With them are Republican volunteers ready to liberate their homeland from Franco.
The Spanish Army in Russia is destroyed in the fighting after Stalingrad and internal dissent rapidly grows in 1944 and 1945 as Spain is isolated from the rest of the Axis.
On August 6th 1945, an atomic bomb is dropped on Hanover with another three days later on Munich. The Reich dissolves into anarchy and its allies are left isolated. American troops cross into Spain in early September with the Republicans and Madrid is liberated on October 1st 1945.
It will take a further two years for the last embers of Nationalist resistance to be snuffed out and by then a Socialist Government rules in Madrid and Franco is dead by his own hand.
Spain joins NATO and eventually the Common Market and acts in 1952 to overthrow the Salazar dictatorship in Portugal.
Eventually, the Socialist Government falls and a new centrist Government takes over inviting the young Juan Carlos back from exile as King.