The first atomic bomb goes off at Los Alamos National Laboratories, New Mexico. This photo, taken from the archives of the U.S. Federal government, shows the bomb itself, codenamed Gadget. It was featured in the opening cinematic of the original Fallout.

The first atomic weapon was dropped on Japan, leading to catastrophic casualties. It was the dawn of the nuclear age, and in a very real sense the beginning of the Cold War.

Japan surrenders to the Allied Powers, marking the formal end of World War II. At this point, Fallout’s timeline and our own are permeable and share some key events. One thing is clear; after 1961, the Fallout universe has almost nothing to do with our own.

As a hedge against communism, the U.S. consolidates political power into 13 commonwealths, each comprised of several former states. The Midwest Commonwealth, for example, includes Minnesota, Wisconsin, Illinois and Indiana while New England — where Fallout 4 takes place — includes Vermont, Massachusetts, Connecticut and all points east.

Destined to become the single largest private contractor to the U.S. government, it's dual focus is on advanced weaponry and biomedical research.

The founder of RobCo Industries, his birth is emblematic of the technological divergence in the Fallout universe — a conceit that gives the Fallout universe its distinctly retro-futuristic style. Curiously, analog technology such as vacuum tubes persisted well into Fallout’s 21st century and magnetic storage tape is still prevalent, leading to room-sized computers. Culturally, it's very much still the 1950s. TVs and radios seem frozen in time at the mid-60s, and radio plays remain popular for decades to come. Meanwhile, atomic power is put to use in pedestrian applications, eventually even powering the family car. Robert House excelled at all of these technologies, helping give birth to many of the universe’s robots including Mr. Handy and, yes … even the Pip-Boy.

Records are hazy, but it's assumed Robert House enrolled at Massachusetts Institute of Technology when he was 18. After graduation he founded RobCo industries. After the Great War of 2077, MIT went underground transforming itself into the secretive organization known as The Institute — which plays a significant role in Fallout 4.

Oil reserves begin to run dry world-wide. Europe invades the Middle East.

An atomic weapon destroys Tel Aviv, Israel, leading to a nuclear exchange between parties in Europe and the Middle East the following January.

The U.S. Government commissions 122 nuclear-proof bunkers to house selected elements of the population in the event of all-out nuclear war.

With the Middle East completely dry, vehicles around the world come to a halt, soon replaced by extraordinarily expensive electric and fusion-powered models. The war in the Middle East ends, and the European Commonwealth dissolves.

Seeking the last remaining oil reserves in Alaska, all out war begins along the Anchorage Front Line. The conflict featured prominently in the Fallout 3 expansion called Operation Anchorage.

The T-45d suit, emblematic of the Fallout franchise — and eventually the standard issue uniform of The Brotherhood of Steel — is sent to Alaska. It makes quick work of the Chinese, whose lines are rolled back but not broken.

Made up of individuals scattered throughout the U.S. government, The Enclave does not expect the vast majority of Americans to survive a nuclear holocaust. Instead, they make plans to move the President somewhere safe when war inevitably breaks out and ensure the continuity of government above all else. They take control of a vast oil field below the Pacific Ocean, which they fortify with armaments and technologies in the hope of using it as a base from which to repopulate the country after the radiation subsides.

Colonel Robert Spindel, Captain Roger Maxson and their men arrive at West Tek's research facility in California to formally investigate their work on behalf of the U.S. government.

Capt. Maxson discovers that West Tek is using military prisoners to test the Forced Evolutionary Virus (F.E.V.), a potent biological agent that mutates its victims in bizarre ways. Maxson orders the West Tek scientists executed.

Over a period of two hours the world burns. While no one knows who struck first, nearly every nuclear power launches their warheads. The land itself becomes plastic from impacts so powerful they cause the Earth’s fault lines to shift, creating mountain ranges and oceans where there were none before. It’s at this moment that the story of Fallout 4 begins.

The Enclave retreats to the privately owned Poseidon Oil rig, situated atop the secret reserves in the Pacific Ocean, with the President of the United States. Under his authority they will continue to be a force in the Fallout universe, eternally engaged in a crusade to rid the wasteland of inferior species and return the U.S. to its former glory by whatever means necessary. Due to their close pre-war ties with nearly every major element of the military industrial complex, they continue to develop advanced technology, including powerful weapons and power armor, well into the 23rd century.

In the Fallout universe when some humans are exposed to radiation they don't actually die, but instead become zombie-like, necrotic creatures called ghouls. For instance, all of the inhabitants of Vault 12 in Bakersfield, California are turned into ghouls.

Capt. Maxson and a small band of survivors at the West Tek facility survive the Great War largely unscathed. Soon, they travel for weeks through the desert, eventually arriving at a government fallout shelter called Lost Hills. That journey came to be known as the Exodus. There, Maxson founds the Brotherhood of Steel, a quasi-religious group of highly militaristic warriors.

The ghouls from Vault 12 that didn't go insane found a city in the wasteland called Necropolis. It's a major location in the original Fallout. Many populations of ghouls around the country do the same. Some ghouls live for hundreds of years, and carry with them pre-war knowledge.

Richard Moreau (aka Richard Grey), a resident of Vault 8 exiled for murder, leads a team of scientists into the now-abandoned West Tek research facility. One of the only survivors of the expedition, he is slowly simmered in F.E.V. for months, turned into a blob-like creature that expands by absorbing other creatures whole. No longer truly human, it begins to call itself "the Master" and over the course of years experiments on any humans it can find. These experiments lead directly to the creation of super mutants — hulking, greenish monsters immune to disease and radiation. Virtually immortal, they are also completely sterile.

The Fallout series began on the West Coast at Vault 13, one of the last of the 122 vaults to be constructed and one of the few which was actually sealed before The Great War. The Overseer, Jacoren, sends the player character — referred to as The Vault Dweller — into the wasteland to find a replacement water chip to repair a faulty purification system.

The Vault Dweller defeats the Master, and saves Vault 13 by returning with a water chip. In a cruel twist, after a year-and-a-half away from home, the Overseer banishes The Vault Dweller to the wasteland, where they found the village of Arroyo.

Now considered to be non-canonical, Bethesda still relies on Tactics for some flavor elements. This combat-focused game tells the history of an expeditionary group from the Brotherhood of Steel who travel East from their base in the desert in search of the remnants of the U.S. government. However, their blimp crashes near Chicago stranding them in the Midwest. Years later, players march a small squad of those same Brothers out of their fortress to free a village from raiders.

Developed by Interplay, this action role-playing game was made for the original Xbox and the PlayStation 2. It takes place around Los Angeles. Given its linear format and narrative liberties, the game is considered to be non-canon by both Bethesda and many fans of the series.

Nearly 70 years after it was founded by The Vault Dweller, the village of Arroyo experiences a terrible drought. Players take the role of The Chosen One, sent out from their village to retrieve the Garden of Eden Creation Kit, or G.E.C.K. With it they hope to create a lush, green oasis in the wasteland. Players travel to Vault 13, which has since been destroyed by The Enclave, a secretive organization with ties to the former U.S. government that predates The Great War. The game ends with The Chosen One saving refugees from both Arroyo and Vault 13 from The Enclave.

Searching for their lost brethren (who became stranded during the semi-apocryphal events that led up to Fallout Tactics), a Brotherhood unit makes its way across the country to Washington, D.C., only to find it overrun with super mutants.

More than 180 years after The Great War, the first Bethesda-developed title in the Fallout series begins inside Vault 101. The player character is named The Lone Wanderer.

That journey leads players to search the wastes around Washington D.C. to find The Lone Wanderer's father, James. Along the way they activate Robert House’s secret project, a massive robot called Liberty Prime, and reactivate The Purity Project — a water purification system that brings clean water to Washington from within the ruins of the Jefferson Memorial.

New Vegas tells the story of The Courier, a mysterious figure sent to deliver a mysterious package. The game has four distinctly different endings, each with its own consequences for the city of New Vegas.

Your adventure starts here.