The Great War开始于2077年10月23日, 仅仅持续了两个小时. 是谁首先动用的核武器已不可考, 不过辐射2中的Dick Richardson总统在和Chosen One的对话中暗示可能是中国先使用: "...然后该死的中国就发射了...". 在战争开始的两个小时内, 世界受到了毁灭性的打击, 这场核战争造成的破坏比以前所有战争的总和还多. 因此尽管持续的时间非常短, 这场战争仍旧被认为是摧毁世界的第四次世界大战(能源战争为第三次世界大战).
The Great War
在美国, 西海岸是首先受袭的地方, 而东海岸由于稍晚受袭(大约9:48, 辐射3中所有时钟均停在这一时刻), 使得更多的人能躲进避难所或其他掩体而保住性命.
两小时的核战争中, 世界地图几乎要被改写. 无论山脉丘陵都在核武器的巨大破坏力下发生了变化. 而河流与海洋则受到了严重的放射性污染, 遍布全球的放射尘给地球带来了长时间的核冬天, 生态系统濒临崩溃边缘.
在辐射3中, 能看到地下铁路系统中有许多人类居住过的痕迹(像是些桌椅). 这可能可以解释为什么地表在宛如地狱的环境中仍有人存活, 还能重建一些文明. 同时, 地下铁道中无数的僵尸也可能是这些在绝望中躲入的普通民众.
大约在核战争之后的一个星期下了一场雨, 随着雨水降下的却是泥灰, 放射性尘埃及各种致命化学品. 这场雨标志着放射尘降的开始. 雨持续下了很多天, 灭绝了数以千计的物种, 包括动物, 植物和微生物. 而幸存者—不论是什么—则要开始在废土上挣扎求存.
Citizens did not heed the air raid sirens, as they believed it was just another drill. The Vaults sealed themselves in (not including Vault 12, which was never intended to shut) as the Earth burned. A few citizens that took the air raid sirens seriously, but did not have access to vaults, made their way to various locations that they felt would be safe from the bombs, like sewers and subway stations, fallout shelters (which were incomparable in regards of protection compared to the vaults), or in the case of the Keller Family, the National Guard Depot. However, without a very strong outter shield to defend them from both the blast and the heat of the blast (such as Lamplight Caverns or Raven Rock), very few would survive, and a few became ghouls, and these ghouls, in turn, formed their own communities. The US Government likely maintained a presence separate from the Enclave on the mainland following the war, as various signs of failed cleanup attempts can be found in the Capital Wasteland. It would seem that some families actually survived a couple of years in drainage centers, as seen after activating the radio signal Oscar Zulu, when it is revealed that Bob Anderstien needed help for his family. Those who had already earned their admission into the Vaults went into them. Those who did not, however, were left to the mercy of the bombs and their own nearby fallout shelters. A female ghoul named Carol (the mother of Gob, the bartender in Megaton) in Underworld in Fallout 3 claims "My family did not have much money, so we could not get into a vault." It seems only the moderately wealthy could buy their way into a Vault at the time of The Great War (likely due to the enormous cost of the Vault projects), though, according to letters discovered in mailboxes, many of those who could afford it were not granted space, due to the lack of time Vault-Tec had to build. This is because Washington D.C.'s Vaults were filled to capacity, while Vaults located in states like Oklahoma were nearly unoccupied.
- It could be possible that the aliens are in fact responsible for the war because of their inquiries into the launch codes of American nuclear warheads. This knowledge comes from one of the many alien captive recordings (log 17). This, however, is open to interpretation.
- 战争可能开始于东部时间9:48, 辐射3中所有时钟均停在这一时刻.