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- "It'll be the Seven Hour War, all over again. Except this time we won't last seven minutes."
- ―Eli Vance[src]
The Seven Hour War was a brief, but decisive confrontation between the Combine Empire and the governments of Earth, ultimately leading to a large human death toll and the Combine occupation of the entire planet.
The war itself is never discussed directly in Half-Life 2 but mentioned briefly by Eli Vance in Black Mesa East looking at a small corkboard featuring several annotated newspaper cutouts and images that cause him to reminisce about the events during the war.
After the war ended, local militias and other resistance groups sprung up to combat the Combine's garrison force.
As the Portal Storms between Xen and the Earth raged across the planet, spreading Xen life forms across Earth, this caused the planet's populace to move into cities for protection. By the time of the Combine invasion, most governments on Earth were weakened by the Portal Storms.
Attracted to Earth by the dimensional rift caused by the Black Mesa Incident, the Combine, a vast alien empire, launched an invasive force that overpowered the planet by using the now conquered Xen, a crossroads of different dimensions and its Portal Storms on Earth. They caught the human population by surprise and defeating all of its armed forces in only seven hours.
The Combine used a combination of superior technology and numbers to overwhelm the Human forces. They used the Portal Storms as a means of transporting their forces all around the Earth at the same time.
According to a statement in a newspaper, "Government's abilities to protect their citizens had been stretched to the breaking point by the time the more coordinated Combine force arrived." This statement suggested that the Combine had sent a smaller force ahead of the main army to soften Earth's defenses.
From the same article, the United Nations Secretariat Building in New York was reported to have been heavily damaged from projectiles from space during the war, suggesting that the Combine may have used orbital bombardments.
During the war, the former Black Mesa administrator, Dr. Wallace Breen had discovered a way through unknown means to communicate with the Combine directly. The United Nations then authorized Breen to negotiate peace with the invading extraterrestrial empire by any means necessary. Breen managed to negotiate peace by "saving" the remainder of humanity at the cost of their freedom. Breen was then declared "Interim Administrator" by the Combine, a position that served little more than a political puppet ruler.
In the aftermath of the conflict, the remaining humans were gathered into reorganized city centers, with the world outside of such areas filled with wildlife native to other worlds. This made the exteriors of cities and the regions beyond dangerous if not downright deadly to not only human life but also to the rest of Earth's natural fauna. The rest of the planet was reduced to inhospitable wastelands.
Facilities like Nova Prospekt were opened within the remnants of the remaining man-made infrastructure- their goals being to modify humans, erase their memories, and assimilate them into the Combine's workforce and military.
The Combine also began to exploit the resources of Earth water, which can be seen in chapter Highway 17 and Sandtraps, where piers sit barren on the once watery shorelines where Earth's oceans had once occupied. The Citadel served as the only node to the Combine Overworld and Earth, as the portal storms were no longer furious on the planet, and they could no longer use Xen as a connection.
The Combine, since gaining dominance on Earth, has imposed a "Suppression Field," which serves to inhibit human reproduction. Comments made at the train station during Gordon Freeman's arrival suggest that the Combine has been drugging the populace through their water supply.
At the beginning of Half-Life 2, the G-Man makes a brief reference to the war, telling Gordon Freeman that "all the effort in the world would have gone to waste..." This line is generally understood to be a direct reference to the war, the establishment of Dr. Breen's terror state, and the reasons for Freeman's stasis. Despite Freeman's triumph at Black Mesa, it was theorized that there was nothing that he or the entire human race could have done to save Earth from the superior forces of the Combine empire immediately after the events of Half-Life.
Half-Life 2 begins an undisclosed number of years after this war, and the rule of the Combine has been firmly established. There is, however, some evidence from the Half-Life 2: Episode One official website indicating that Half-Life 2 takes place nearly two decades after the Black Mesa incident. Such a time frame is logically consistent with the aging of the series' characters between Half-Life and Half-Life 2. This time frame explains how Eli Vance's child, Alyx Vance, has matured to an adult since the events of the first game, where she was still an infant at the time.
The reason for why there are no children in the game overall, the Combine had set up a reproductive suppression field for all of the remaining humans a short time after the war, preventing any further reproduction for approximately twenty years until the events of Episode One. However, the suppression field is disabled due to the damage the Citadel had taken thanks to Freeman's actions in Half-Life 2.
- Summary of Half-Life and Half-Life 2 in the official Half-Life 2: Episode One website. Retrieved on August 26, 2006.