I have used this! I am guilty! lol
Okay, its not a bad one but I have used this and it even is one of the center plot lines for the series I have been writing. I will add some description below, but my general thoughts on the trope is very dependent on the situation it is used in and what is preventing a truce or ceasefire from either side. Hollywood in general has a reputation for ignoring the finer details war causes. Resourced put into it, lives lost, frequency of replaceable soldiers, etc. Typically, these forever wars have worked best in cases like Underworld, where the Lycan and Vampire factions have just never gotten along since their uprising and have always been at each other’s throats. It is a war, but its only fought in skirmishes and they both do their best not to get humans involved. This is way more believable than two fully fledged civilizations locked in an eternal war or it drawing out so far that peace was never saught from either side. It really depends on the situation for me.
How I used the Forever War trope
When I ended up using this trope, it was done out of a need to bring some merit and meaning to something that was already present in my works; Balance. This is going to be lengthy so brace yourself but basically, when the universe was created, it was done by two Titans. Cosmic beings that controlled the balance of life and death. They used their power to give an otherwise blank universe life, forging suns, stars, planets, species, etc.
Life, however, is not perfect. Conflict, pain, strife… it was all inevitable. They knew this but they also knew that those kinds of emotions and events, mixed with magic, could have some… well… very unfriendly results. Magic, in this universe, has no light or dark side. Even some of the most barbaric forms of magic can be used to do a lot of good, should the user have the mind for it. However, magic is easily influenced by its surroundings. It can destabilize and weaken spells, or strengthen them. Likewise, a user able to use magic will find that their emotions and feelings are more intense. Sometimes to a point where the overwhelming power mixed with those feelings will utterly break someone completely and they will succumb to their darker desires.
This results in individuals who lean so far into being Too Good or Too Evil that they could not just be left to roam the world. Evil, or darkness, if it won, would utterly destroy all life and return the universe to a bare void. It’s not intended to. Those who are that corrupt aren’t meaning to do that kind of harm. But their power is so far unchecked and unbalanced it is the inevitable outcome they would cause.
Likewise, for those who are too good, if they were to win, life would cease to have any form of conflict and because of this, the meaning of life would fade. There would be no motivation or challenge to be better and life would become stale. Sure, they aren’t TRYING to make that happen. But again, left unchecked, it would be an inevitable result.
Knowing this, the titans created Angels; Celestial beings who were given a number of gifts, strengths, and a unique form of magic whose sole purpose was to watch over the universe and deal with these individuals. This is where the forever war comes in. Their role in the universe has been to safeguard a necessary balance, sometimes requiring them to do some fairly messed up things. But if they did not, they would be risking the complete destruction of the universe in one way or another. To really make this more interesting, I even included examples where the Angels lost faith in what their mission was and even chose not to deal with some situations. The results that came from it were so devastating, that they have had to absolutely obliterate worlds to keep it from spreading. This is their forever war. A war that has gone on since time began that the rest of the universe is mostly oblivious too. Some situations have risen where they had to rally and lead armies of mortals and other creatures against some of their targets. But they aren’t as frequent. Usually, they deal with individuals before they obtain that level of power.