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- This article is about 22nd-24th century migration period. For the SLDF exodus, see Operation EXODUS.
The beginning of the Exodus period is cited as 2102 as that was the year the Deimos Project was put forth on the grounds that FTL travel was possible. Prior to this point, the only colonization attempts feasible had been sublight slowboats, but with successful jump-tests in 2107, the flight of Raymond Bache in 2108, and the TAS Pathfinder voyaging to Tau Ceti IV, the era of Exodus was primed.
The first colony would be established in 2116, and by 2123 advances in KF drive engineering and manufacturing had brought the cost of the hyperdrive down by what is said to be a factor of 100. It is here, perhaps, that the era of Exodus - and in particular, the First Terran Exodus - begins.
Through legislature, the Alliance would attempt to control what would later be referred to as the First Terran Exodus. Their success, however, is debatable, especially in light of both the rapid advance of colonization and entrepreneurs such as Rudolph Ryan. The first Alliance Grand Survey of 2172 reported that within a radius of 40 light years from Terra were over one hundred colonies. By 2235, the sphere of colonies had swelled to more than 600 worlds.
In 2236, the Outer Reaches Rebellion would begin, and the 18-month war would bring consequences that included the eventual fall of the Terran Alliance - as well as the start of the next migration. With expansion came the issue of clear and timely communication across an ever-expanding domain, impeding governance and allowing corruption to run amok.
The Terran Alliance would lose the war without clearly ceding defeat, withdrawing most of their forces over 2238 where bureaucracy didn't strand units such as the 151st Fusiliers, and eventually, with a shift in the balance of power, the expansionists within the Alliance would be trumped by the pro-isolationist liberal party. The result would be the Demarcation Declaration - the Alliance's effective abandonment of all worlds beyond thirty light years from Terra. Thus in the wake of broken industry, shattered economies, and no support, the Second Terran Exodus begins in the year 2242.
The expedition that would become the Taurian Concordat launched within this era, as did the freebooter Theban Legion who would found the Rim Worlds Republic. Within the Alliance itself, in fact, was a period of instability and chaos, economic hardships within borders that had now shrunk and crowded them in. Hence, the Alliance, too, saw a massive surge of emigrants seeking a better life elsewhere.
First Terran Exodus
The First Exodus marked the height of the Terran Alliance. During this era, the first off-system colonies were established.
After almost a century, the hyperspace theories of Thomas Kearny and Takayoshi Fuchida had been proven correct. The Terran Parliament approved funding for the Deimos Project, the development of the first faster-than-light space ship.
The Race to Space
After the maiden flight of the TAS Pathfinder and its arrival in the Tau Ceti system on December 5, 2108, the Terran Alliance began a crash program to produce faster-than-light colony ships. The first such ship was the TAS Ark, which in 2116 established its first extrasolar colony on Tau Ceti IV. By 2123, corporate production of JumpShips had become feasible, and the race to space became the new, global Manifest Destiny.
During this first colonization wave, new planets were settled monthly. Eventually, disaster struck in April 2128, when the privately constructed and operated colony ship Liberator disappeared without trace. The Alliance Parliament quickly passed regulations, forcing colony ships to be escorted by Terran Space Navy ships, and installing planetary administrators as colonial governors.
The Separatist Conflicts
The Terran Alliance of the early 22nd century was still only an alliance dominated by the wealthiest states, not even uniting the entire planet. The sleeping conflict between the Separatist nations and the Terran Alliance not only fueled colonization efforts, but also created an atmosphere of constant threat.
After 2177, the Ryan Cartel's newly developed ice shipping process became the main source of drinking water for colonies, further increasing the pace of colonization. Rudolph Ryan himself was - after his death - revealed as a strong supporter of the colonies' independence and had often "lost" technicians or JumpShips full of colonization equipment in support of budding Separatist colonies, which his corporate subsidiaries had helped create in the first place.
Despite Ryan's support, not all Separatists and anti-Alliance groups emigrated off-world, but radicalized in the face of increasing Alliance oppression. Terrorist organizations like Elias Liao's New World Disciples sprang up. Quickly gaining notoriety, Liao's group was responsible for the death of no less than 26 heads of states, and 14 Terran Alliance Parliament members (and at least 135 bureaucrats, scientists, and technicians), further destabilizing Terra's political system. Rudolph Ryan himself was killed by an anarchist assassin in 2185.
The simmering conflict between the Alliance and the Separatists and the constant threat of nuclear terrorism finally erupted into a series of unification wars. By the early 23rd century, Terra was finally unified under the Terran Alliance. The Alliance itself, now without external opposition, began the slow process of unifying from an alliance of independent states into an actual federal state, although more through inertia than by design. 
During this period of consolidation, the Alliance Parliament (stuck somewhere between a discussion chamber and an actual legislative body) polarized into two opposite political parties - the authoritarian Expansionists and the slowly radicalizing Liberals. The Expansionists had informally been in power since the development of the Hyperdrive, while the Liberals had begun imitating the tactics of their successful opponents. 
Collapse and Isolation
The final Grand Survey, conducted in 2235, listed 628 colonized worlds in a radius of 250 light years. In May of the same year, Denebola declared independence, and just a year later, the Outer Reaches Rebellion began on Freedom.
While local protection treaties, such as the Chesterton Trade League had already been established for decades, the Alliance-appointed colonial governor's demand for extensive regulative rights was - in the face of the Alliance's overall benign neglect - the driving force behind an independence movement that rose to power in several loosely aligned colonies. When Terran troops first fought the well-entrenched insurrectionists, they were soundly defeated, to the shock of the Expansionists on Terra. 
The conflict continued well into 2237, with more and more declarations of independence reaching the Terran Alliance Parliament. Saddled with passive resistance and refusal of support from other colonies, the Terran forces finally realized the futility of their situation and returned home. 
Following this first defeat and with others soon following, the political situation on Terra turned into chaos, allowing the Liberal Party to oust the Expansionists in 2240. Unfortunately, the Liberals had become as radicalized as the Expansionists, and acted accordingly. For a while, even mentioning Terran offworld colonies was treated as a criminal act. Finally, the Liberals passed the Demarcation Declaration: from 2242 onward, all Alliance colonies beyond 30 lightyears of Terra granted independence, whether they desired it or not. The age of the First Exodus was over.
Amidst inexperience, shattered industry, and mangled economies, many would leave the post-rebellion colonies on a the Second Terran Exodus.
Second Terran Exodus
With the Demarcation Declaration ending the First Exodus, the Second Exodus marks the transition of the Terran Alliance into the Terran Hegemony, the rise of the Great Houses, and emergence of most Periphery nations.
With the damage inflicted during the Outer Reaches Rebellion left unhealed - broken industry, ravaged economies, and wounded populations - many felt that there was nothing to rebuild from. When the Demarcation Declaration then cut off all colonies beyond 30 lightyears of Terra, many of the dispossessed felt the only viable action was another migration - another exodus.
The Calderon expedition, for example, would take 25 JumpShips and over 2300 volunteers from Aix-la-Chapelle, and over a 22-month journey would reach the edge of the Hyades Cluster. By January 23rd, 2253, Samantha Calderon would christen the planet Taurus, blossoming eventually into the Taurian Concordat. Elsewhere, the Theban Legion of Hector Rowe would flee for six years through the Dark Nebula, and the freebooter squadron would found the Rim Worlds Republic on September 8th, 2250.
- This page is not currently complete!
- The Exodus Era is said in some cases to end by 2314 with the start of "Consolidation", and in other cases with the era of the Terran Hegemony. Both encompass the same major historical points.
- In 25 Years of Art & Fiction, the Terran Exodus is stated to begin in 2242, whereas many earlier sources indicate that there was the First Exodus in the 22nd century, with the Second Exodus - or at least, a second mass migration in the Inner Sphere - occurring due to the Demarcation Declaration.
- MechWarrior, First Edition, pp. 3-4,"A History of Human Space, 2001-3025: Exodus (2102-2313)"
- MechWarrior, Second Edition, pp. 107,"Historical Overview: Exodus (2102-2313)"
- DropShips and JumpShips, pp. 9-14,"Space Travel in the Successor States: Exodus"
- The Periphery, 1st Edition, pp. 12-16,"History: First Exodus"
- Era Digest: Age of War, pp. 8,"The United Hindu Collective"
- The Periphery, 2nd Edition, pp. 5-6,"The Periphery: In the Beginning"
- BattleTech: 25 Years of Art & Fiction, pp. 19,"Timeline Entry, 2242"
- Field Manual: Periphery, pp. 7-8,"Settling the Fringe"
- The Star League (sourcebook), pp. 8-12,"History: Terran Alliance: Politics of Colonization"
- Jihad Hot Spots: Terra, pp. 144-145
- House Liao: The Capellan Confederation, p. 8
- Handbook: House Davion, p.19
- House Liao: The Capellan Confederation, pp. 9-10
- BattleTech: 25 Years of Art & Fiction
- DropShips and JumpShips
- Era Digest: Age of War
- Field Manual: Periphery
- Handbook: House Davion
- Handbook: Major Periphery States
- House Liao (The Capellan Confederation)
- Jihad Hot Spots: Terra
- MechWarrior, First Edition
- MechWarrior, Second Edition
- The Periphery, 1st Edition
- The Periphery, 2nd Edition
- The Star League (sourcebook)