Oh ye, the outlawing of losing wars. Not very convincing for adults but I guess teenagers think it sounds cool.
I don't think it is a good idea to give the soldiers the impression that they will fight to the last man, since that encourages killing their officers at an earlier stage than they would otherwise. Preferably, you want to lure with some peace agreement that is just around the corner, such that the soldiers believe that there is hope for them.
If Sweden ever were to surrender in war it will most likely be broadcast by the prime minister and/or the king/queen (Sweden is a constitutional monarchy). Until such a time and until such a message is confirmed we'll just assume that Sweden has not surrendered.