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Opposing Force cover

Opposing Force cover.

"Government cover-ups were not in my job description!"
―HECU soldier[src]

This article describes the Half-Life: Opposing Force storyline, chapter by chapter.

The story of Opposing Force cleverly interweaves with the events of Half-Life, so that the player catches a glimpse of Gordon Freeman, the main character from the original game. Shephard sees an officer making a pivotal radio broadcast that Freeman overhears in the first game, and visits some recognizable locations.

In the original Half-Life, a Resonance Cascade opens an extra-dimensional rift, which causes Xen aliens to teleport into the Black Mesa Research Facility. The surviving scientists and security guards at the facility struggle to escape. Responding swiftly, the United States military initiates a massive "clean-up" operation to eradicate the alien presence at Black Mesa as well as "silence" any witnesses.

Boot Camp (optional)


The G-Man observes Adrian Shephard and two of his fellow Marines training.

The training chapter of Opposing Force. Adrian Shephard is bumped to the top of the Advanced Training list. Shephard and his comrades are trained by Dwight T. Barnes, Marine Drill Instructor, in Santego Military Base, Arizona. He works his way through the training exercises overlooked by Drill Instructor Sharpe until he is ready for the field.


  • Easter egg: in the dormitory where the level starts, each trunk bears the name of a Gearbox employee, such as Randy Pitchford, Stephen Bahl, Rob Heironimus, David Mertz, Landon Montgomery, Patrick Deupree, John Faulkenbury, etc., mirroring the Easter egg from Half-Life in the locker rooms of the Sector C of Black Mesa.
  • Other Easter egg: the room right below Shephard's dormitory exists but can only be accessed by noclipping. Inside can be found an Easter egg, consisting of initials and a date ("DMM 1999"). "DMM" is the signature of Santego Military Base's designer, David Mertz, Gearbox employee. "1999" is the release date for Opposing Force.
  • Yet another Easter Egg: When leaving Shephard's dormitory you can overhear Drill instructor Barnes talking to another recruit, he says "Texas? Only two things come from Texas," this is a reference to Full Metal Jacket.
  • This is the only level in the original Half-Life games that does not take place on Black Mesa territory nor on Xen.

Chapter 1: Incoming

Opposing Force intro

Goose 3 under attack by an Alien Aircraft.

As the game begins, Shephard is part of the clean-up operation. After his transport aircraft is taken down by an Alien Aircraft and he is cut off from the rest of his unit, the "clean-up" mission is abandoned and Shephard joins forces with the scattered survivors seeking escape.

Before the first chapter of Half-Life: Opposing Force, a short introduction is shown. As Adrian Shephard and his fellow HECU comrades are approaching the LZ (Landing Zone 117) at the Black Mesa Research Facility, his plane (codenamed Goose 7) is shot down by Alien Aircrafts, along with several other V-22 Ospreys (the first one is codenamed Goose 3). The rest of the opening sequence consists of Shephard continually losing and regaining consciousness, seeing a conflict between the Xen aliens and the Marines who survived the crash.


  • The canyon wall from the first part of the Half-Life chapter Surface Tension, which Gordon used to get to the Lambda Complex, can be seen.
  • The chapter name "Incoming" is given in the "titles.txt" file.
  • This level most likely takes place at the same time as either "Office Complex" or "We've Got Hostiles" in the Half-Life storyline.
  • It is possible to obtain the MP5 if the player is quick enough. To obtain it, the player must jump on the plane and go to the marine that is behind the plane being attacked by Vortigaunts and Alien Grunts. However, the marine may sometimes survive this attack, preventing the player from getting the MP5. Also, the plane won't hurt the player if he stands on it.

Chapter 2: Welcome to Black Mesa


Scientists are carrying a wounded HECU soldier.

Welcome to Black Mesa3

The collapsing floor.

After the crash of his V-22 Osprey, Adrian Shephard regains consciousness completely in an infirmary, not too far off from the crash site. He leaves the infirmary, learning that the other Marines who had survived the crash had been killed by the aliens. He makes his way towards the extraction point, where he is told via radio that the military forces are pulling out of the facility.


  • Takes place at the same time as the Half-Life chapter Surface Tension.
  • The Blue Shift and Decay storylines have most likely ended before this chapter.

Chapter 3: "We Are Pulling Out"

We Are Pulling Out3

The HECU evacuate.

Half life gman 3

The G-Man preventing Shephard's escape

As the battle begins to turn into the Xen aliens' favor, Shephard and the remaining HECU troops begin to evacuate Black Mesa.

Adrian Shephard attempts to reach the HECU's extraction point to escape Black Mesa. He has first eye contact with the mysterious Race X that seems to be collecting humans for study in their world. Shephard reaches the extraction point but is deliberately left behind due to the G-Man's actions.


  • This chapter occurs near the end of the Half-Life chapter Surface Tension. The radio operator heard at the end of Surface Tension appears just before the end of the chapter, meaning that Gordon Freeman reaches the Tactical Map by the time Shephard arrives at the operator's room making the announcement.

Chapter 4: Missing in Action


Xen flora invading Black Mesa.

Adrian Shephard continues his journey through Black Mesa in search of both his comrades and an alternative escape route after being abandoned at the extraction point. After battling Vortigaunts and traveling through a zombie-infested blast furnace, Shephard meets several other Marines from his company who have also been left behind. He joins forces with them as they try to escape from the facility.


Chapter 5: Friendly Fire

Massn bomb truck

The Black Ops loading the nuclear warhead into a truck.

Friendly Fire4

The rocket from which the warhead was taken.

After battling through an office complex filled with Vortigaunts, Adrian Shephard and other HECU soldiers' attempt to find and use an old transit system to escape to the Lambda Core. The Black Ops are first introduced in this chapter as well. Shephard comes across them in a hangar where they are loading a nuclear warhead into the back of a truck. Adrian then learns that the Black Ops soldiers have been sent to kill the remaining HECU Marines and cover up the Black Mesa incident. Shephard meets up with several other surviving marines and fights the Black Ops, eventually reaching an underground railway system that leads to the Lambda Complex.


  • The chapter's title is a reference to the fact that HECU and Black Ops are technically on the same side (being from the same country), yet the Black Ops openly engage any HECU personnel they encounter.
  • Takes place at the same time as the Half-Life chapter Lambda Core.
  • In an office, two dead scientists can be seen lying in front of their desks. Their names are S. Reardon and S. Jones, a nod to Gearbox employees Sean Reardon and Steven Jones.
  • In another office is a picture of Gordon Freeman labeled "Employee of the Month".
Employee of the Month

Gordon Freeman's "employee of the month" picture.

Chapter 6: We Are Not Alone

Sprites xen

Adrian's first view of Xen.

Chapter 6 serves as a short interlude in the game with reminders of events from the original Half-Life. Arriving at the Lambda complex, Adrian Shephard sees Gordon Freeman being teleported to Xen. Shephard is also forced to travel through Xen to find a way out of the Lambda complex.


  • Takes place at the same time as the last moments of the Half-Life chapter Lambda Core and the other Half-Life chapter Xen.
  • A Chumtoad is hidden in a vent towards the beginning.
  • Running quickly, the player can follow Freeman through the portal, but Shephard will end up falling to his death in Xen and get the message "Evaluation terminated: Subject attempted to create a temporal paradox". Also, when entering Xen, a filename "C4A1TITLE" will appear as a title. This is because the game reuses the Xen map from Half-Life, and no chapter title is defined in Opposing Force's "titles.txt" file. This can be fixed by adding the missing entry to the file.
  • In the second map of this chapter. The Scientist will die, float or stand for the following reasons:
    • If the player stands under the scientist that is falling before he hits the ground, Shephard will die because of the high-speed collision against the scientist. However, the scientist will get stuck in a falling animation.
    • When the player uses the god cheat command.
    • When the player throws something ( not powerful ) to the floating scientist.

Chapter 7: Crush Depth

Crush Depth2

Shephard rescues a scientist.

In it, Adrian Shephard finds himself in underwater laboratories where several Ichthyosaurs are being held. After making his way through the labs and freeing a scientist who provides him with information on the area, Shephard is again forced to teleport to Xen and back again to reach a new part of Black Mesa.


  • Takes place during parts of the Half-Life Xen chapter as well as "Gonarch's Lair".
  • Crush Depth in fluid physics is the depth at which the pressure will be strong enough to crush something; therefore the name is a pun to the design of the level itself, which has a considerable amount of water in it.

Chapter 8: Vicarious Reality

Vicarious Reality2

The Barnacle Grapple is explained.

Vicarious Reality

Shephard fighting a Voltigore in the Sector E Biodome Complex.

Adrian Shephard is traveling between various biosphere chambers and laboratories featuring massive terrariums used to house Xen fauna being studied by the scientists deep within the Sector E Biodome Complex. Eventually, he reaches an older industrial area and picks up a radio transmission from a group of Marines fighting some kind of massive creature.


  • Takes place at the same time as the Half-Life chapter Interloper.

Chapter 9: Pit Worm's Nest

Pit worm damn it hurts

The Pit Worm is defeated.

Details Adrian Shephard's battle with the monstrous Pit Worm blocking his progress in Waste Processing Area 3. Working his way through the surrounding area (littered with the corpses of the Marines who sent the distress signal in the previous chapter), Shephard manages to dump toxic waste on the Pit Worm, killing it and allowing him to access the next area.


  • This chapter mirrors the chapter Blast Pit from the original Half-Life, though it is much smaller.
  • The puzzle to kill the Pit Worm involves both a "valve" and a "gearbox" to be used, which are obvious references to the game's developers as an Easter egg.
  • Another Easter egg is the garbage compactors, especially the flooded one, which are directly designed after the Death Star's garbage compactor seen in the film Star Wars Episode IV: A New Hope.
  • In the first map, a flooded Xen area where one can be brought by the Displacer features two dead scientists. In the second map, another scientist can be found clinging to the edge of an island with another Displacer (that brought him there) still on the island.
  • Takes place at the same time as the Half-Life chapter Nihilanth.
  • The Pit Worm battle can be skipped by jumping from the pressure valve platform on the left to the platform behind the Pit Worm that would normally open a bridge after defeating the Pit Worm.

Chapter 10: Foxtrot Uniform

Foxtrot Uniform4

Two Shock Troopers and a Voltigore attacking Adrian Shephard and his comrades.

Foxtrot Uniform 3

Shephard encountering a Baby Voltigore in the darkened canals of Black Mesa.

Details the fierce battle raging between the Race X creatures, the Black Ops contingent, including several snipers, and the remnants of the HECU in the last hours of the Black Mesa Incident. Adrian Shephard makes his way through the underground canals and sewers of Black Mesa, fighting through a Voltigore nest, and arrives at the hydroelectric dam featured in the first game. Here, a Gargantua has been trapped on top of the dam and several Marines are attempting to kill it. Shephard uses explosives to destroy the creature and leaves the area through the dam's exposed water pipes.


  • The name of the chapter is based on the NATO phonetic alphabet, Foxtrot being "F" and Uniform being "U". This is a euphemism for either "fuck you"[1] or "fucked up," depending on the context it is used in.

Chapter 11: "The Package"

The Package2

A Black Ops Apache.

This chapter details Adrian Shephard's discovery of the mysterious Black Ops' plan for Black Mesa. He finds them in an underground parking garage, activating the thermonuclear warhead from the fifth chapter, apparently with the intent of destroying the facility. Shephard kills them and deactivates the nuclear bomb, but later sees the G-Man reactivating it. Adding to the Black Ops, Shephard must face heavy artillery, a black AH-64 Apache, and Shock Troopers.

  • The Half-Life's storyline ends at this point.

Chapter 12: Worlds Collide

Gene Worm defeated

The Gene Worm is defeated.

After making his way through warehouses filled with Race X creatures and Black Ops fighting, Adrian Shephard arrives at an old industrial area of Black Mesa deep underground where the enormous Gene Worm is attempting to come through a portal from the Race X homeworld. Shephard uses mounted laser weapons to blind and kill it; in its death throes, an enormous teleportation portal spreads outwards and envelops him.


G-Man Xen Op4

The G-Man talking to Shephard in the Osprey.

Shephard regains consciousness inside a V-22 Osprey, confronted by the mysterious G-Man. As the G-Man talks to Shephard a white flash occurs in the distance, indicating that Black Mesa has been destroyed by the nuclear warhead. The G-Man then informs Shephard that he will be detained "in a place where you can do no possible harm, and where no harm can come to you." He explains this is done since Shephard reminds him of himself but is still a dangerous witness. The G-Man walks into a portal, Shephard is detained and the end credits roll.


  • This ending sequence mirrors that of the original Half-Life.
  • Easter egg: If the player uses a console command to view the skybox from within the V-22 Osprey during the G-Man sequence, there is a hidden message on the upper skybox texture. The message reads: "HACK HACK HACK ALL DAY LONG. HACK HACK HACK WHILE I SING THIS SONG [sic]."[2] This poem is a reference to Adam Sandler's song, The Beating of a High School Janitor. This can also be found by viewing the game files. It probably references to the fact that the player has to "hack" the game to see the text, as in using the console.