This has been off-topic for a while...
Today they have good relations with all potential threats, the international system adds deterrence (every aggressor would have a severe political loss) and its military is strong enough to signal sovereignty.
On top of that they're in NATO and EU, the two most powerful alliances in human history. What endangers them the most today is the excessive disrespect and aggressiveness of their allies, which can drag Portugal into conflicts just as excessive disrespect and aggressiveness of an ally dragged Germany into the First World War.
I suspect you have an exaggerated idea of deterrence.
Deterrence does not require to ensure defeat or destruction of an aggressor. It merely needs to turn an aggression into an undesirable scenario for the potential aggressor.
In some cases this means that the mere fact that an aggression wouldn't directly turn into an occupation (~Czechoslovakia), but instead lead to a messy resistance (official and covert, ~Finland and ~Iraq) would deter. You gotta get this into the potential aggressor's head, of course.
Stupid aggressors are stupid - some people only learn through pain.
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