Is it possible, in any case, to unite Spain and Portugal into a single nation? It would have to be between 1910 and 1930, so Spain is still a monarchy and Portugal is a republic. Could anything make this happen?
Calm yourself, it has only been 40 minutes.
To answer your question, only a direct military conflict that resulted in the annexation of Portugal would be plausible. Unless if the monarchy is restored and the King of Portugal places himself under Spanish rule.
Hmmm... What could lead to a direct military conflict?
Is it necessary to be before 1930?Hmmm... What could lead to a direct military conflict?