Swedish military doctrine was (and I expect remains) that: a) it is impossible to prevent the enemy from attempting an attack; b) we can make it as painful as possible to them, and our goal is to repel the invader from Swedish soil within days; and c) we will immediately mobilize all resources in the country to fight back, bringing hundreds of thousands of soldiers into their pre-assigned positions within 24 hours, abandoning all economic activity for the sake of total defense, so that whatever the enemy thought was a benefit in attacking Sweden, it will have been completely nullified.

Switzerland had a similar doctrine, and communicated it explicitly to potential invaders in the 20th century: try to invade the country and we will destroy all means of transportation in the plains, withdraw the army into mountain fortresses (e.g. air bases literally built inside mountains with tunnels serving as landing/take-off strips), and keep attacking you until the ends of time. Also, Swiss men keep their military rifles at home, with sufficient munition to fight their way to their assigned base in case of war.

It is interesting that neither country has been attacked over the last several hundred years, even while surrounded by fighting parties during WW II. I think armed neutrality is a beautiful thing.