Well thankfully Franco is either dead or dying and Spain starting her transition to democracy so that should defuse the possibility of direct Spanish intervention. They're still likely to be nervous though so expect the military to be moved towards the border and the various police and intelligence agencies being very vigilent. The US is not going to like this so I could easily see the CIA starting up a destabilisation programme as soon as possible. With Spain no longer Francoist that should give them enough cover to be able to base themselves out of there, and whilst Franco is gone the various right wing supporters are still in positions of power so they're likely to co-operate either officially or unofficially.
The Soviet Union is going to be very happy. Not sure what if anything substansive they're going to do though, perhaps we see Soviet vessels making a lot of port calls. For NATO Portugal is going to be out, the other member states are likely to suspend co-operation with them at the very least, and Spain is likely to become a member much faster than the seven years it took in our timeline. Depending on how friendly/aligned this new Portugal is with the USSR we could be seeing a lot of new US/NATO bases in Castille-Leon, Extremadura, and Andalucia.
Franco is no longer the one calling the shots (for the record, he ordered to bomb and/or mine the path of the Green March and nobody gave a shit) but that does not mean that 1975 Spain is a demoracy or that it will not intervene.
Arias Navarro plain told Kissinger that he was ready to invade Portugal if he had the blessing of the USA.
While short and in Spanish, the article is worth a read because it touches a lot of interesting points. The Portuguese Revolution had scared Arias and he paralysed further reforms at the time. Meanwhile, the government was at odds with Washington because
it though that it was supporting Morocco in the Sahara and that it was not working to let Spain enter NATO any time soon. Of course, this was because other European countries flat out refused to have Spain in either NATO or the EEC, and every leader of a democratic European government who pushed for the cosideration of ally to a regime born with Nazi and Fascist assistance was bound to get gang-raped in the next elections. I suppose Arias was trying to kill 2 birds with one stone and try to erase both the threat of a communist government in Portugal and to get better relations with America. The Americans hand could be forced because 1975 was also the year (by pure coincidence!) when the continued existence of American bases on Spanish soil was set to be re-negotiated.
I suppose Dr. Strangelove would be the man to ask about this, but I see Arias embarking in this war as the swan song of the dictatorship - especially if the Americans actually don't make a big commitment. Even with the Portuguese army divided, the African wars had left Portugal with a big, trained army -
twenty times larger than the peace time Spanish army if we take
this Wikipedia map seriously. So most of the troops would have been draftees taken from the same young college-aged guys that are rioting for political freedom and reforms. An invasion would spark nationalism and act as an unifying factor in Portugal, and fail to do the same in Spain since there is no way to portray this war as defensive (unlike, say, a war with Morocco). Meanwhile, France is a safe heaven for opposition groups and could care less if they are armed and get their gadgets there or not, and there are the effects of the recent 1973 oil crisis to care about. To top that, the Francoist government itself is divided.
Needless to say, this should have big consequences.
