It was possibly already done long ago, but did anyone had idea, or made something about the Spanish Civil War reaching Salazar's Portugal?
And I means it in a large potentialities range - be it by example a local opposition to Salazar appears or grow in courage due to the Republicans's fortune changing by the frontier regions, and starting an anti-Salazar civil war... OR Republicans attacking by error or design portugese forces in a border incident, OR Nationalists hunting Republicans hidden in Portugal somehow.. etc...
you can link me, of course.
Well, nationalists wouldn't need to hunt republicans in Portugal. Portuguese authorities willfully handed them to nationalist forces in OTL. Combining the diplomatic and political support given by Salazar to Franco, plus the participation of portuguese volunteers in the nationalst forces, we can say that to a extent the SCW touched Portugal.
The only way I can see a further effect of the SCW in Portugal is in a scenario where general Rojo's "Plan P" is properly executed and successful. In short, the idea (conceived just after the republican victory in Guadalajara) was to launch a great offensive through Extremadura, considered the weaker point in the nationalist front. The objetive was to reach the portuguese frontier, cutting the nationalist zone in two and separating Andalusia from the rest of the nationalist forces, depriving them of their main route of supplies, which started in the port of Seville. At the same time, it would force the nationalists to reduce their pressure over other fronts. The plan included also diversionary actions in Andalusia, some of them really ambitous, including an amphibous operation against Motril, in the province of Granada. It considered also the possibility of popular uprisings behind the nationalist lines, since Extremadura and Andalusia were traditional left-wing strongholds and nationalist repression there had been specially harsh.
But what is important for this thread: in order to make all this effective, it was assumed that Portugal should respect the non-intervention pact and wouldn't allow nationalist troops and supplies to move through its territory. And this "should" wasn't an assumption of Salazar's goodwill and neutrality, but a more open "should", if you get me.
In the words of Rojo himself it would be "
convenient to prepare forces of Carabineros (frontier police) (...)
with enough firepower to respond in the event of the most intense violation of the portuguese neutrality by the enemy" It was also suggested to ask for international observers to grant that portuguese neutrality was respected. It's important to note that when it's said "violation of portuguese neutrality by the enemy" it means portuguese cooperation with the nationalists.
Now, our problem is to make the Plan P successful. On one hand, it was a victim of the political internal struggles amongst the republican factions, and thus posponed twice. On the other hand, when it was executed, or at least a part of it, it was during the battle of Peñarroya, the last serious battle of the war. What happened then followed the lines of other republican offensives. Large territorial gains in the first phase, with the troops proving that they had managed to act coordinated and according to the plans (not a small achievement, considering the origins of the republican army) followed by their innability to hold the gained territory and neutralize nationalist counter-offensives, due in part to a fatal lack of initiative by the part of the republican NCO's.