I've seen several times people saying that main themes for Fallout games are sacrifice for Fallout 3 and Letting go for New Vegas. I am not quite sure it is those, but there might be some factors i didn't take into account. Beside, it might be interesting to dwelve into other titles and try to see what would be the main themes of those stories. Fallout 1 : Imo, this game is greatly shaped by the impact of the great war, and for many factions, there is the notion of that the human race shouldn't be allowed to make the same mistake again. For quite some of them, it boild down to the concept of free will and the need to remove or alter it. The Master wants to make everyone part of the unity. The children of the Cathedral want you to be devoted to them. The Brotherhood of Steel want to remove the most dangerous weapons from the common wasteland population, and used their free will to defect from the army. Vault 13 Overseer want to remove unwanted influence on his decision to keep everyone in the vault. Quite often, those who want to remove free will from others have the best intentions in mind, but sometimes have a flawed reasoning. It is not like they want to remove it for the sake of it. Fallout 2 : Contrary to Fallout 1, which often had the lawfull vs mobster clash, most Fallout 2 settlements are into a corner in which they have to change, make compromise, associate themselves with people they don't like, not because they think it is right, but for their survival. Vault City and Gecko are the opposite but need each other to survive. Broken Hills seems an heaven where all race works together, but they don't like each other, and even if you make peace, they will all leave once there is nothing to gather here. Redding has to make a deal with one big city, even if they will lose something in any situation. The mutants have to become peacefull and forfeit the unity if they want to survive, but that doesn't mean they aren't nostalgic. The main antagonist is a faction that specifically refuse the change. They want to remain exactly how they were before the war, and refuse any compromise that would make them co-exist with people they don't like. They prefer killing everyone in the world, than accept that said world has changed. There also a bit of free will on the opposition between the lawfull and safe but boring Vault City and the unlawfull and dangerous, but fun New Reno. But i am not sure this theme go further in the rest of the game. If it is only a local theme, it doesn't matter here. Fallout Tactics : It has been quite some years since i played Tactics, but from what i recall, there is a lot of situations dealing with the concept of safety and its cost. Safety is what the Midwestern Brotherhood of Steel (or MBOS) provides in other to assimilate nearby settlements and make them lose part of their identity. Also, it is an important trait of General Barnaky character. The man lost his wife agains't mutants and wish to bring into the world the safety he couldn't provide for his wife. His wish for safety creates many problem if he is allowed to rule in one of the endings. But said safety is also needed to build upon a new advanced society and push back the calculator army. And safety is also the reason for said Calculator army to exist in the first place. They remove the treat of hostiles, by removing all potential hostiles from the earth. Fallout 3 : I find this one a bit harder to look upon. I only played once and i found it extremely messy. It has a fetish with pre-war times, like to blend storylines together without finishing them, and doesn't seems to prioritize its plots. You looks for a father that is half a blank state, work on a project that isn't needed by the wasteland population and makes allies without convincing them, then fight enemies that want the same thing you do. There seems to be quite some focus in the past, and how new characters and factions want to correct the mistakes of the past, on a small extend. Hope and looking forward seems to be quite recurrent occurences. By the end of the game, the good faction has beaten the bad faction, there is a new book about survival (certainly don't want to dwelve on that), there is more trade routes (that don't go anywhere ingame), more pure water (even if people were drinking and healthy before, beside the two water beggars), at a small cost of human life. Fallout New Vegas : So many things could happens and there is so many factions blend together that it is a bit harder. I would say the devellopers compare many kind of leadership. There is the democracy, the feudal system, anarchy and our current corporatocracy with House, and there is a bit of their inner working, but it doesn't say much plot-wise. The intro of the game introduces us to the fact that dices are rigged from the start and that the power holders rarelly show their cards and that most of the game is played under the table. Casino could conveys the thing that you rarelly win when you try to play agains't the system (as seen with the Khans and the Kings). So power itself might be a theme on it own. Power to make your own rules. Power to make others play according your rules and appropriately lose. There is also the pyramidal structure, with usually the best part of the bargain took by the leader and those who understand his inner and hidden rules the best, and the worst to the enemies AND the grunts who blindly follow the public rules of the faction. So the deception is often at play. Contrary to Fallout 2, the people from the settlement aren't necessary forced to change if they want to survive, thanks to the Yes man option, so the compromise is there, but not always a necessity. Also, power, greed, and fanatism often blind people from serving the true purpose of the faction they are part of. NCR is losing itself for oligarchy. Caesar own successor don't play the same rules. Many nightkins seeks for a master surrogate, regardless if the entity is defending the values of unity. The BOS became fanatics (and Father Elijah became the exact opposite of what the BOS stand for), the families and other tribes lost their identity, and so on. So, we have many people trying to stick to a faction without seeing that the faction isn't the same as it was meant to be. So, instead of having to accept a change like Fallout 2, many factions went into decline and decadence without even being aware of it, because they refused some changes. It feel somehow, like the opposite of Fallout 2. Fallout 4 : Didn't play it. Fallout Brotherhood of Steel and Fallout Shelter : Didn't play them enough. (nor intend to) Will probably try to expand later. I doubt i've seen them all. There are problably some you did see and i didn't.