The Fallout world follows an alternate time-line of real world history. Up until the Great War in 2077, the Fallout world was dominated by the 1950s culture, even with the rapid technological progression. The Fallout world setting is heavily influenced by the science fiction anthology Worlds of Tomorrow, which was released during the Golden Age of Science Fiction.
The Great War is the single event that has shaped the Fallout world into its current form. On October 23, 2077, the United States, China, and other countries bombarded each other with a rapid exchange of nuclear missiles and bombs lasting two hours. The destruction caused by the brief nuclear war was staggering; more energy was released in the early moments of the war than in all previous conflicts combined.
The Fallout games take place years after the Great War as humanity struggles to survive and rebuild. Some groups have barely managed to survive above ground, either scavenging the scorched ruins of cities or surviving and adapting through mass mutation. Communities that were sealed in underground Vaults during the war are now emerging to re-populate the blasted landscape. Striving to organize and sustain the human race, these tattered remnants of civilization are threatened by psychotic mutants, rogue machines, raiders, and all manner of hostile creatures. The first two games take place mostly in the area known as the Core Region, where the main threats so far have been the Master and the Enclave, while the third game takes place in the Capital Wasteland on the East Coast.