Mountains and rivers gave good defenses, when they did go to war guerrilla warfare and a hostile population made things difficult, and the fact that Portugal had a lot of wealth from colonies as we’ll probably made their army strong enough to survive.
Couldn’t have conquered, they would he stuck in a horrible guerrila war all while still fighting the republicans. If anything it would just mean that the nationalists lose. Spain could not invade anyone, there is a reason they stayed out of ww2.
Spain was very close to invading Portugal. Until Saviour intervened.
It would've been horrible with Portugal ending up losing. Portugal balanced by supporting both sides.
While franco won, he begged him not to join ww2 in the fear of invasion.
You overestimate Nationalist Spain. They barely managed to take over their own country. A two front war would mean certain death. They had no real planes either, and their tanks were not effective in the rivers and natural defenses they’d have to cross. Their untrained milita would fail in Portugal as unlike in their Homefront they don’t understand the land they are invading. Spain had no real offensive potential and expanding the war may make France and the UK intervene. Would not happen, and if it did it would be an anticlimactic failure.