This article contains spoilers. Read at your own risk!
It might spoil your gaming experience when first playing the related games.
- "We should thank Our Benefactors for giving us respite from this overpowering force. They have thrown a switch and exorcised our demons in a single stroke. They have given us the strength we never could have summoned to overcome this compulsion. They have given us purpose. They have turned our eyes toward the stars."
- ― Wallace Breen, addressing citizens' concerns about the Combine negating human reproduction.[src]
The Combine, abbreviated as CMB, and referred to in propaganda as "Our Benefactors", is an immense and powerful inter-dimensional organization. Comprised of both allied and enslaved species, the Combine's collective goal is to dominate and absorb the Multiverse into its inter-dimensional empire; the Universal Union. The Combine are the main antagonists of Half-Life 2.
The Combine Empire sprawls across multiple parallel universes, and includes an unknown number of sentient species. Details of the Combine's leadership and administrative structure remain unknown. On Earth, aliens called the Advisors are responsible for facilitating and overseeing all communication and interaction with the Human race.
The Combine manipulates species through a variety of means, including bioengineering and artificial implantation. The products of the Combine's re-engineering process are known as "synths", bio-mechanical organisms that serve a variety of functions within the empire. The Combine also use their technology to create armies of super-soldiers, uniquely adapted to the particular environments of the conquered worlds. This process results in a highly mobile and adaptive military force which is able to respond to any threat and crush any opposition.
Vocal stress is placed on the first syllable. The name is pronounced COM-bine, as in Combine harvester, as opposed to the verb form com-BINE, as in "to join together or unite." Dr. Breen refers to the Combine Soldiers and Civil Protection as "The Transhuman Arm of the Combine Overwatch"  in Nova Prospekt, verifying that "Combine" is an accepted name of the empire, even by the empire itself.
It is unknown how many worlds the Combine has under its control; it is known that in addition to Earth, the Combine invaded the home-world of the Nihilanth's species. The defeated Nihilanth escaped the onslaught and sought refuge in Xen. It brought with it members of a number of enslaved or allied species, including the Vortigaunts.
Subsequent to the invasion of Nihilanth's unnamed home-world, Earth became the Combine's most recently known annexation. Following the Black Mesa Incident; it was acquired following Earth's surrender at the end of the Seven Hour War. Following the standard Combine process, members of Earth's dominant species were modified to form a new arm of the Combine military. In addition to forming the bulk of the Combine garrison on Earth, in-game dialogue suggests that units of the Transhuman arm of Overwatch are also deployed across the Combine Empire in a "permanent off-world assignment". Assignment on other worlds is considered a horrible fate for Overwatch soldiers unfortunate enough to be stuck with it and is often used as a punishment. Equally dire is the threat of "permanent off-world relocation". Judging by dialogue from Breen, many of the territories under control by the Combine are nigh-uninhabitable by humans without special life support systems.
Despite the highly advanced technical capabilities of the Combine, they appear to have a relatively limited grasp of teleportation technology. Dr. Mossman explains that while the Combine can teleport from one universe to another, they do not know how to teleport between different locations in the same universe. The teleportation method developed by Black Mesa enables same-universe translocation, and as a result the Combine is eager to obtain information on their teleportation technology. Dr. Mossman actually helps the Combine build a teleporter with such capabilities in Nova Prospekt, but it is destroyed during Alyx and Gordon's escape.
The Combine's method of teleportation appears to be highly inefficient compared to Black Mesa's equivalent; a large amount of power and massive pieces of machinery are required to perform teleportation, as seen at the end of Half-Life 2, where Dr. Breen attempts to escape from the Citadel using a Combine teleporter. This teleporter requires a dark fusion reactor to power it, while the teleporters designed by humans require relatively small amounts of power and very little machinery in comparison. Xen teleporters appear to require almost no machinery or energy of any kind.
While the physics of teleportation are poorly explained, it is known that Xenian teleporters use Xen as a "dimensional slingshot," bouncing off of one universe to another and from one location in a certain universe to another in the same universe. Combine teleporters cannot do this, instead having to "tunnel" through dimensions to the target universe.
Combine on Earth
Invasion of Earth
Following the Nihilanth's demise, the Combine found that it was able to use the portal storm that was occurring at the time to reach Earth, where it launched a massive invasion that culminated in the Seven Hour War. Statements made by the G-Man suggest that the human race was unable to mount any effective resistance to the Combine armies and that Earth's military forces were almost instantly overwhelmed.
Combine dominance on Earth
The Combine rules Earth from a massive structure known as the Citadel, this one being in City 17, where Dr. Breen runs his operation. At the end of Half-Life 2, as Doctor Breen attempts to teleport off of Earth using the dark fusion reactor, a massive portal is created and, through it, several buildings that resemble Citadels are visible.
At the start of the game, the Combine appears to have almost complete dominance of the remaining pockets of civilized Earth and does not identify who Gordon Freeman is. However, Doctor Breen immediately informs a Combine Advisor of Freeman's appearance during a teleport accident, in which Gordon Freeman appeared in Doctor Breen's office for a brief amount of time. Only a handful of rebels, loosely organized in a ragtag resistance, are secretly opposing the Combine. Gordon Freeman's actions after his return eventually inspire a massive insurrection against the Combine in City 17, which results in a full-scale street war between the citizens and the Combine forces.
The reasons behind the Combine's desire to control the Earth are unknown, other than the absorption of Earth's resources, the use of human teleporter technology and the enslavement and exploitation of its dominant species - the humans - for either menial work or military service, considering that "permanent off world assignment" is threatened to soldiers who fail in their attempts to kill or capture Gordon Freeman throughout the game.
The Combine, since gaining dominance on Earth, has imposed a "suppression field," which serves to inhibit human reproduction. The field prohibits the formation of certain protein chains that are vital to human embryonic development; this has effectively reduced the global human birth rate to zero and has ensured that the humans currently alive will be the last generation.
Doctor Breen addresses this issue to the people via a broadcast during the early levels of Half-Life 2 as the response to a letter written to him by a "concerned citizen." Avoiding answering the question itself, Breen explains that he believes the field is a positive influence, as it supposedly nullifies one of mankind's basest, most instinctual urges; he claims that the field will be deactivated once the humans prove that they "no longer need it."
During the game, Resistance members occasionally make humorous remarks about the suppression field, such as "When this is all over, I'm gonna mate." It was initially thought that the suppression field somehow prevented human sexual urges, mainly due to Dr. Breen's statement that it was suppressing "the urge to reproduce," but this statement may, in fact, be referring to the suppression field's physiological effects causing human "urges" to diminish rather than to stop outright.
In Half-Life 2: Episode One, it is revealed by Dr. Isaac Kleiner during his transmissions throughout the city that the suppression field has been disabled with the near destruction of the Citadel. He says that everyone who has escaped City 17 "should do their part" in the re-population of the human species "before the Combine attempt to restore their dominion." When Alyx Vance hears this, she remarks "Is Dr. Kleiner really telling everyone to... get busy?" Eli Vance jokingly gives Alyx and Gordon a similar suggestion, claiming to want grandchildren. This is a strange statement, as in the first game Gordon is at least 20 years old, where as Alyx was a newborn child. It may show knowledge about Freeman's stasis between HL1 and HL2.
Mind control and memory replacement
Comments at the train station at the start of Half-Life 2 suggest that the Combine has been drugging the populace through their water supply. One of the citizens remarks "Don't drink the water... they put something in it, to make you forget. I don't even remember how I got here." This is not mentioned elsewhere, but the idea is reinforced by the numerous soda machines stocked with "Dr. Breen's Private Reserve," which freely dispense water in a standard 12-ounce can.
The insinuated reason for this supposed mind control is so that humans forget why they hate the Combine, and will willingly accede to its (and Breen's) demands, and to create a fresh mental template for forced re-education.
In addition, a Combine radio transmission to Civil Protection officers states: "Reminder, memory replacement is the first step to rank privileges." This could explain why none of the CPs are able to join the Resistance after the Uprising (apart from Barney Calhoun, who was a double agent for the Resistance to begin with); their memories may either forbid them from harboring any negative thoughts toward their Combine overlords or program them to believe that the Combine must be protected.
However, Barney suggests the opposite when, during Episode One, he states that "now it looks like we're gonna have to cut a path through every chicken-shit Metrocop who's having second thoughts about defending City 17!" What this could mean is the Combine presents an illusion of free will by promising privileges to CPs willing to give up their memories, despite their loss of humanity, and the possibility that the Combine just takes CPs into Nova Prospekt without their knowledge.
Information about forced memory replacement can be found in the game's data files, specifically this model (above) named "
soldier bed," seen later inside the Citadel during Episode One. This model closely resembles that of concept art in Half-Life 2: Raising the Bar. The machine itself consists of Combine emitters and equipment; attached is an arm-like device holding a human body. Lastly, a shell-like apparatus containing three different screens and panels envelops the head. Accompanying this model is a small group of sounds resembling harsh subliminal messaging; this audiovisual messaging system explains the military training used by normal post-human individuals.
This model, in addition to several bizarre sounds of voices in the data files, suggests that this "brainwashing" memory replacement is an important part of the Transhuman operation. The process of erasing memories, Combine propaganda, and eventually, memory replacement results in a soldier incapable of rebelling against the Combine influence, as well as enabling Transhumans with no military background training to become part of the Overwatch forces.
The Combine does not flinch at committing acts of extreme brutality and even genocide in order to maintain control over the human populace. In the Half-Life 2 Chapter Route Kanal, a refugee base is raided, and a few members of the base are lined up against the wall and shot just as Gordon arrives. The town of Ravenholm was shelled with the intention of killing all residents, and throughout the Highway 17 chapter, the player encounters numerous bodies in the houses of the coast, including some that have been burnt by the Combine in a bonfire.
The absence of children
It is obvious that the children are missing in Half-Life 2 and its episodes. The main reason is the placement of the Suppression Field by the Combine, right after their victory at the end of the Seven Hour War. Given that the Combine has been occupying Earth for nearly twenty years, the humans that Gordon sees throughout the game are possibly the last humans born naturally.
Evidence such as the ghostly laughs and screams of children that can be heard in the playground outside one of the apartments in the first chapter, a crying couple that can be seen shortly thereafter, the fact that the player does not see any children in the most human-populated areas, remarks by Resistance members such as "I'm glad there's no kids around to see this," and the presence of discarded toys such as baby dolls can be seen during the game, but they are only reminders of the past.
According to Half-Life 2: Raising the Bar, children were present in the early stages of the game development, in an area of City 17 called the Combine Factories. Adults and children were to work in this area closely watched by Metrocops and Combots. In the Cremator Factory, children were building Cremators. As the concept of human reproduction being disabled by the Suppression Field evolved, children finally got cut with the whole area, along with the Cremator.
Depletion of Earth's resources
It is evident at several points in the game that the Combine is depleting Earth's natural resources.
One of the official Half-Life 2 descriptions details how Gordon Freeman must return to "an Earth infested with aliens and being picked to the bone." 
One of the most noticeable signs is that Earth's ocean levels have dropped dramatically. This can be seen during the coastal chapters Highway 17 and Sandtraps, and the waterways of City 17 in Route Kanal and Water Hazard. The coastline is littered with boats and ships resting on what was previously seabed, and there are various docks and piers that are no longer standing in water, but instead standing on the old seabed.
At the beginning of Highway 17, Gordon arrives at a harbor which is now a considerable distance from the water's edge. Indications of the previous sea level can be judged by moss that had previously gathered on harbor structures at the edge of the water, but which now lies several feet higher than the ground level.
It is mentioned in the book Half-Life 2: Raising the Bar that this massive, planet-wide water drainage is accomplished through the presence of a giant Combine "drain," actually a teleporter, which sends the water to other Combine-enslaved planets.
More generally, parts of the game world are flooded with parasitic Headcrabs and toxic waste, making them generally inhospitable to human life. Infrastructure is either decaying (as with Highway 17, which is in a state of incredible disrepair and littered with old rusting cars) or rendered completely useless (as with Nova Prospekt, where the traditional prison area is mostly flooded and run down, if not outright destroyed by the explosion at the end of the chapter Entanglement).
Animals are rarely seen inside and outside of City 17, suggesting that they are critically endangered; though, strangely, birds are the only animals that are seen in Half-Life 2. The Fisherman in Lost Coast comments that there is no fish left to eat, only leeches that devour anyone who steps into the ocean, posing a further threat to humanity.
Additionally, City 17 itself is being devoured, as Combine Walls spread outward from the Citadel, consuming the city's buildings. It is unknown whether the Combine is purely using this method to destroy the city, or whether it is actually gathering raw materials from the city's structures.
During the development of Half-Life 2, the Combine originally had a huge industrial facility that was referred to as the Air Exchange, which gradually absorbed Earth's air and replaced it with chemicals and other murky gases which were harmful to humans, but most likely ideal for an environment that the Combine master race could inhabit. It was up to Gordon Freeman to travel to the Combine Air Exchange after the prison levels. Gordon's actions at the Air Exchange were to trigger the human insurrection against the Combine in City 17, but as the level was dropped, this was instead made to happen due to Gordon's actions at Nova Prospekt.
The Combine heavily relies on imagery through logos, symbols, and propaganda posters to assure their influence on Earth and remind its residents of their presence. Combine units - humanoid and Synth - also bear insignias, logos, and other markings. Many Combine posters are also scattered around City 17 and its sector (including the Coast, Nova Prospekt, etc.). Most of the time they include two common Combine symbols, with variants in color and image backgrounds. Most Combine imagery is quite abstract, and the intended messages can be very subtle.
Breencasts are regular broadcasts made by Dr. Breen, delivered to the populace of Combine-controlled towns and cities via private televisions and, more commonly, large video monitors mounted on walls in public places such as town squares and railway stations. As the messages simply loop, it is possible that all announcements are pre-recorded. A few citizens in the first chapter can be heard saying that the messages are pre-recorded.
Combine military technology
The Combine use the technological growth of other civilizations against them. Weapons, vehicles and other technology are assimilated into the Combine armory; the Overwatch utilizes Earth's small arms, armored personnel carriers, trains, and helicopters, often re-designing them for greater efficiency. Most of Combine's military units on Earth are either Human or originated from Humans, like Overwatch Soldiers. Other vehicles and machines used by the Combine are clearly of non-human origin; examples of this are the Strider and the Gunship, both of which are derived from living creatures that are possibly Transbeings of other enslaved civilizations.
Nova Prospekt, while a Combine stronghold, has only a little evidence of occupation. The building itself and its coastal defenses are just recycled human structures, thrown together almost hastily. Indeed, most areas used by the Combine feature little unique architecture.
The primary military force of the Combine on Earth is the Combine Overwatch (referred to by Doctor Breen as the "Transhuman arm of the Combine Overwatch", although he could be referring to the entire Combine military presence on earth as the Overwatch and the ranks including modified humans are the Transhuman arm.): humans who have been modified into "Transhuman" (or "post-human", as referred to by Dr. Kleiner) cyborgs. They are the most frequently encountered foes throughout Half-Life 2. Although primarily used on Earth, it is mentioned that they are also deployed to other Combine territories throughout the empire, whether willingly or as punishment.
It is important to note that Civil Protection units are not hybrids and are in fact, human.
- Civil Protection: The quasi thought-police that patrols the cities, monitor the public airways, and conduct randomized raids. Since little modification is involved, some Resistance members, such as Barney Calhoun, join Civil Protection in order to go undercover to investigate Combine activity and tip off would-be victims.
- Overwatch Soldier: The main military of the Combine on Earth. Soldiers patrol and enforce Combine law outside of the city boundaries. It includes the Shotgun Soldier and the Nova Prospekt Prison Guard.
- Overwatch Elite: The Elite soldiers of the Combine Overwatch. They have undergone extensive modifications and are seen protecting the Citadel or occasionally leading squads of regular soldiers.
Synths are creatures that, over a course of imposed evolution and alteration by the Combine, have come to fit a particular niche in the Combine military. Once self-replicating organic creatures that originated from different worlds, they were enslaved and assimilated into the Combine to become the backbone of their military.
Various types of Synth have been brought over to Earth by the Combine. It is likely that Synths were the primary forces used by the Combine during the Seven Hour War, as the human-derived Combine units, as well as technology such as hunter-choppers and APCs, would have only been developed after the Combine's rule on Earth had been established.
- Crab Synth: Never actually fought, but seen in Half-Life 2 in the Citadel, files, and the Half-Life 2 Beta.
- Dropship: Primary troop and weapon transport of the Combine.
- Gunship: Assault aircraft that usually fight in groups of two for protection.
- Hunter: Medium ground assault units, similar to Strider, but still quite different.
- Mortar Synth: Never actually fought, but seen in Half-Life 2 in the Citadel, files, and the Half Life 2 Beta.
- Strider: Large ground assault units used by the Combine. Walks on three incredibly long legs, towering over the battlefield.
Combine Combat Technology
The Combine employs numerous devices and weapons that are used in the day-to-day policing and surveillance of the general populace. Some of these are merely human inventions that have been re-designed by the Combine to better suit their purposes, while others are either original, or re-designed technology of other civilizations.
- Manhack: Essentially, a flying, autonomous circular saw capable of tracking targets.
- Rollermine: A ball-shaped 'mine' with a rudimentary targeting system that, once activated, follows anything it identifies as a threat and subjects it to electric shocks. They can also attach themselves to vehicles such as the Scout Car.
- Hopper Mine: A programmable explosive device that hops into the air and explodes when approached by an enemy.
- City Scanner: A flying security camera and scout that takes pictures of enemies and relays their location to its command center. Also "dive-bombs" its target if subject to enough incoming fire. Occasionally used as a spotter for Striders.
- APCs: The main mode of transport of Civil Protection, is a common sight within the cities. They are armed with a missile launcher and a mounted pulse rifle.
- Hunter-Chopper: Piloted by two members of the Overwatch, this vehicle is primarily used to track down solitary members of the Resistance, or small groups of Resistance soldiers. Heavily armed and armored, it features a pulse cannon and can saturate an area with mines.
- Razor Trains - Combine trains made to transfer Combine Troops, supplies, and prisoners to locations.
- Headcrab Shell - They deploy in the resistance outpost and base areas, especially in the Uprising as it is a very common sight in City 17 and the Outland.
- Sky Shield - Referred to in Overwatch radio chatter, "Sky Shield" is some sort of military surveillance technology used by the Combine. Overwatch soldiers report their target or are given targets through "Sky Shield", which may be a satellite array of some sort.
Most examples of Combine structures are very large and imposing, with very blocky, monolithic shapes with sharp angles made of a dull, blue-gray metal. Various tubes, wires, and pipes can be seen running throughout gaps in the walls and down along corridors and tunnels. Their buildings are purely functional with no thought given for aesthetics or comfort, with no embellishments or decorations shown save the occasional sign or Combine logo, and bright but sparsely-placed artificial lights create harsh, dark shadows throughout the Combines' complexes. Steep, deep drops and platforms lacking guardrails are common too; most likely due to the Advisors' ability to fly and thus having no need for bridges, although bridges can be seen in places where Combine soldiers move and operate; another example of the Combine's assimilation of human technologies.
- The Citadel - The large building looking after City 17 and Combine forces.
- The Depot - A Combine building looking after prisoners at Nova Prospekt.
Behind the scenes
- Originally, the Combine were to use Earth's building materials and twist them to make their own buildings. This resulted in odd designs, such as the Citadel's interior being made out of ceramic tiles. This was cut for the familiar metal used by the Combine in the final version.
- Some Combine units were cut from the final version of Half-Life 2 for various reasons, such as redundancy or unsatisfying game-play. Some were recycled into other units seen in the final version. These cut enemies include the Combine Assassin, Combine Elites, Combine Sniper Elites, the Alien Assassin, the Conscripts (Though the conscripts would later become allies and assist the rebels after the Air Exchange is destroyed), the Cremator, the Combine Guard, Combine Synth Elite Soldier, the Alien Combine Soldier, the Combine Super Soldier, Combine Mobile Mine and the Sacktick.
- During the E3 demo, the Citadel is referred to as "the Combine", implying that the Citadel could originally have been the Combine.
List of appearances
- Half-Life (Nihilanth's appearance evidence only) (Retcon)
- Half-Life 2 (First appearance)
- Half-Life 2: Lost Coast (Non-canonical appearance)
- Half-Life 2: Episode One
- Portal (Indirect mention only)
- Half-Life 2: Episode Two
- Half-Life: Alyx
- ↑ 1.0 1.1 Half-Life 2: Raising the Bar
- ↑ 2.0 2.1 2.2 Breencasts
- ↑ Marc Laidlaw Vault on HalfLife2.net
- ↑ 4.0 4.1 PC Zone magazine, September 2005.
- ↑ Marc Laidlaw's e-mail on Xen, Planet Half-Life Mailbag.
- ↑ Half-Life 2 - as stated by the Overwatch Voice
- ↑ Half-Life 2 Walkthrough - Chapter 5: Black Mesa East. Planet Half-Life.
- ↑ Half-Life 2: Episode One. Chapter: Urban Fight
- ↑ Half-Life 2 on Steam