The Seven Hour War

== The Combine Invasion of Earth ==
The Seven Hour War was a brief but devastating conflict that unfolded on Earth, forever altering the course of human history. Spanning a mere seven hours, this cataclysmic event had occurred due to multiple different reasons in numerous timelines, usually from a space-time blip called a Portal Conduit.
Within a particularly significant universe; the Black Mesa incident acted as a gateway with the Combine and their subsequent invasion in the Seven Hour War.
== The First Combine invasion of Earth ==
=== The Freeman Dimension ===
The first time the Combine Empire had invaded Earth was within the Freeman Dimension, which comprises the events of the Half-Life games.
==== Aftermath of the Resonance Cascade ====
After the tumultuous short-lived invasion by the Nihilanth, the Black Mesa Research Facility was destroyed by a modern Air-to-Ground Nuclear Missile, levelling the site and leaving much of it's surroundings destroyed and inhabitable. While the Nihilanth's invasion was cut short by Freeman, the many thousands of his invasion force remained on Earth. This included the intelligent Vortigaunts, few Controllers, clone Grunts, and many Xen fauna such as the Houndeye and Headcrab. There were other species as well, the wall-growing barnacles, and the Antilons, who originally shared a Homeworld with the Vortigaunts.
While the Vortigaunts remained passive to the humans shortly after the end of the invasion, the animalistic Xen wildlife, grunts and Antlions ravage New Mexico, with their random-acting force spreading quickly to state lines. After Freeman closed Black Mesa's side of the portal, It was common for the Nihilanth's precision strikes to fire out-of-control, not only landing Xen troops and Wildlife outside of the Black Mesa Facility, but far from it, as far as the neighbouring Russian landmass.
=== Portal Storms ===
==== Portal Storm Definition ====
===== Xen Portal Storm =====
While the Resonance Cascade produced 'Portal Storms' across planet Earth, it was not to be confused with a Dark Energy portal storm, which was caused by the collapsed Dark Fusion Reactor after the destruction of the City 17 Citadel.
Meteorological Portal Storms caused by the Resonance Cascade were green in colour, lasting all the way up to the Combine's suppression field post-Seven Hour War.
Before Freeman had closed the Nihilanth's end of the interdimensional gateway, the Portal Storm had served as a random permeator of Xen wildlife, antlions, and the dedicated invasion force; this affected the entire North American Continent and a small portion of the Asian continent, exclusively; Russia.
===== Dark Energy Portal Storm =====
For a brief period during the Seven Hour War, the Combine's Superportals had reacted with the ongoing Portal Storms that had been raging since the Incident, this had caused some of their own portal's to exhibit brief Portal Storms of their own; this gave the Combine Forces a strong encouragement to deal with the problem at hand as swiftly as possible. 
During Scorched America, the Combine had completely glassed New Mexico and the surrounding stately areas, levelling not only the ruins of Black Mesa to an even lesser state, but leaving the United States in deeper turmoil.
A few Dark Energy Portal Storm's were encountered after the fall of the City 17 Citadel, as the Combine had purposely detonated the Dark Fusion Reactor to initiate a new Superportal for backup during the larger Resistance Uprising conflict.
==== The Portal Storms ====
The effects of the Resonance Cascade had allowed the powerful Nihilanth to open a tear between Xen and Earth, to pour his troops through for his full-scale invasion, however, despite Freeman's efforts to close both ends of this portal, the Resonance Cascade's effects far out-reach these consequences alone. Earth was permanently crippled, and had caused severe meteorological events, spreading from New Mexico to the rest of the world. These events were called 'portal storms', terrifying quakes of electromagnetic energy, which could shake entire cities and kill a-many with devastating death tolls. 
These were the months leading up to the Seven Hour War, where not only were the human race shocked by the existence of extra-terrestrials, but had their planet torn asunder by the global catastrophe of continent-sized storms. With the death toll rapidly climbing into the millions. In order to mitigate the damage and ensure the survival of as many people as possible, the world governments devised a plan and convened a summit to address the crisis.
The central focus of the plan was the consolidation and fortification of human populations within the sturdiest cities and urban centres around the world. Recognizing that dispersing resources and manpower over a vast expanse would be ineffective, the decision was made to concentrate efforts on a select number of strategic locations. These cities possessed the infrastructure, defences, and resources necessary to withstand the ongoing onslaught and offer a semblance of protection to the populace.
=== The Seven Hour War ===
After only two months post the devastating Black Mesa incident, the invasion force of the Combine had came from seemingly nowhere, this was in fact not true, as the Combine had breached through to Earth-space by detecting the Resonance Cascade, or an 'invasion blip'. In the early wake of the conflict, Combine Superportal's opened up above Earth, and in the lower atmosphere, military strongholds were bombarded from orbit by starships of the Combine's Grand Navy and subsequently, more dedicated bomber-craft, and the following invasion was lead by the Synth Corps, with towering Troops, Hunters & Striders to spearhead the ground ops, to the fearsome Gunships and Advanced fighter aircraft to dominate the skies.
The Combine forces neutralized both alien and human targets in the conflict, with the most brutal campaign of the war, Scorched America, where the entirety of New Mexico and it's surrounding states were glassed to indefinite inhospitality. The nuclear storm-engine that was the ruins of the Black Mesa Research Facility served as the source to these Portal Storms, nevertheless, they continued to rage on, to a slightly lesser degree.
=== Humanity's Surrender ===
Dr. Wallace Breen, the former administrator of Black Mesa and controversial member of the Emergency World Summit, had gained contact with the Combine in the final hours of the Seven Hour War, signing humanity into an unconditional surrender and forfeit subjugation to the mysterious invasion force. Breen was appointed Interim Administrator of Earth, with Earth-bound Combine forces under his command.
In the following weeks and the aftermath of the Seven Hour War, a few military units of different countries had continued the fight, whether unknowing to the surrender, or upholding the will to never give up. Many of these stragglers were caught and executed, with a lot of survivors going into hiding. These survivors would form the backbone of the future Resistance.
The Combine occupation officially begun a month in, as things continued to calm down, the Combine begun issuing extremely basic rations in the form of water, but lacked the knowledge of what humans may eat. Willing humans were rounded up by the Synth Troopers into urban centres, where any resistance was met with a field execution. Many of the original invasion force had disappeared in the intervening months, and a crude Nexus for Combine Operations was built in the ruins of New York, where Wallace Breen would act as human-combine relations for humanity.
This was a period for a lot of people to escape the grasp of the Combine, and to flee from their sight, as there was an extreme lack of infrastructure across the many now-ruined cities. Not only were many of Earth's cities in disarray, but the need for Combine-specific infrastructure was needed. Synth engineers were brought in via the Combine Portal on the Dreadnought ships' personal Portal Generators to begin the construction of the first Citadel of Earth. Along with the construction of the Citadel, humans were encouraged to aide the Combine's efforts, setting up the Civil Worker's Union, with the promise of benefits for those who cooperate. Many humans did do so, with a strange incline of Loyalists, a term for people who were willingly loyal to their Combine overlords.
The engineers, with the help of the now-established Civil Worker's Union, begun to reinstate infrastructure within the cities across the globe, in place of future Citadels, Nexus' were built as temporary base operations and a centre for ration control. One of the innovative designs of the Combine's subjugation techniques were their Smart Barriers, built from the Combine's signature metal, Smart Barriers were tall, robotic structures that would move based on the current flow of threat surveillance & local data, these would prove as the boundary of what was inside a Combine City, and what was not. Combine Smart Barriers work not only as a boundary-marking fortification, but as a defensive counter-measure as they were frequently known to crush aliens or people that were not supposed to be near them, that is, if they were detected.
The City of New York was designated as City 1 and the construction of the first Citadel had finished by five years of the occupation through mass-transport of materials from the remaining dreadnought, almost all of the original invasion force had been returned to their original deployment locations off-world, with only a handful of Synth Troopers remaining as a backup regiment. A big problem for both the Combine and the human race post-The Seven Hour War was the dominant presence of Xen wildlife, the Antlions and the continuing presence of Portal Storms. With the completion of the first Citadel, The City 1 Suppression Field came online.
These Suppression Fields were blanket-repairs used by the Combine to halt many problems at once. It had disrupted the Antlions sensory organs in the form of the Thumper, a vibration-creating device deployed in sandy areas, where the Antlions thrive. 
The Suppression Field is also the name for the invisible field that makes humans infertile, along with sharing the name with the advanced Dark Energy Mortar, which was used to 'suppress' targets on a battlefield.
In need of an Earth-based military force, a policing program was setup in place of the former Synth Troopers, where humans could sign up for improved rations and housing, and insurance for the safety of their families, this police force was called the Civil Protection. From here, the Combine-occupied Earth became more independent over time, leading to the creation of many other Citadels, and the feared Overwatch Transhuman Arm.