Half-Life: Opposing Force

Half-Life: Opposing Force is an expansion pack for the popular first-person shooter Half-Life, developed by Gearbox Software and released by Valve Software on October 31, 1999. A stand-alone version was also included with the release of Half-Life: Blue Shift. The expansion's single-player mode features the same setting as the original, with the twist that the player is cast not as Gordon Freeman, but as Corporal Adrian Shephard, a U.S. Marine. Shephard is sent into the huge underground Black Mesa Research Facility on an undisclosed mission, but things go wrong and he finds himself fighting for survival against sinister government agents and monstrous aliens. The title "Opposing Force" has a dual meaning, referring to Newton's law of Opposing Forces as well as the fact that the character you play, a Marine, was one of the adversaries of Gordon Freeman in the original Half-Life.

Although only released for the PC, a Sega Dreamcast port exists as a homebrew release.



The action of Opposing Force interweaves with the events of Half-Life. In the original game, a "resonance cascade" opens a 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. As the game begins, Shephard is part of this operation, as part of the HECU (Hazardous. Environment. Combat. Unit) Company. After his Osprey is shot down 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.

As the tide of the furious battle begins to favor the alien army, Shephard realizes the military forces have been ordered to pull out. In the midst of the battle, however, a mysterious new enemy appears, known by fans as Race X. This collective of races appears to not be associated with the Xenians, and show hostility to them. The Black Op forces (seen only briefly in the first game) are acting independently of the Marines, and intend to destroy the entire complex with a thermonuclear warhead. Shephard deactivates the bomb but later sees the G-Man reactivating it. After defeating the monstrous Gene Worm alien, Shephard finds himself back in a V-22 Osprey transport, similar to the one he was on at the beginning of the game, with the G-Man. The nuke at Black Mesa detonates and the G-Man detains Shephard someplace where he can tell no one of what he has seen and cannot be harmed, pending further evaluation.

It is possible to roughly correlate the timeline of the events in Opposing Force with that of the original Half-Life through a few events common to both, particularly a radio transmission ordering the abandonment of the base (heard from a receiver by Freeman in Half-Life and at the transmitter by Shephard in Opposing Force) and Shephard's entry into the main teleporter chamber just as Freeman, in a cameo appearance, leaves for Xen a few meters away.


  • Intro - As Corporal Adrian Shephard and his squad are approaching the LZ (Landing Zone 112) at the Black Mesa Research Facility, his Osprey (call sign Goose 7) is shot down by Xen Manta Rays (aka Flyers), along with several other V-22 Ospreys (first one is codenamed Goose 3). His commanding officer on board falls through the open door of the transport during the attack, seconds before he is able to give the squad their secret orders. The rest of the opening sequence is seen in quick scenes as Shephard, injured when his plane went down, drifts in and out of consciousness. A rapidly decreasing number of Marines who survived the crash try to fight off the Xen aliens, but seem to be beating a retreat by the time he blacks out entirely.
  • Welcome to Black Mesa - Shephard wakes up 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 or driven off by the aliens. He makes his way back to the wreckage of the transport, where he is told via radio from the Commander-in-Chief of the unit that the military is pulling out of the facility.
  • "We Are Pulling Out" - Shephard ventures through Black Mesa towards his assigned extraction point, fighting mutated security guards and has first eye contact with the mysterious Race X that seems to be collecting scientists for study in their world. Shephard reaches the extraction point, but is deliberately left behind due to the G-Man's actions.
  • Missing in Action - Shephard continues through Black Mesa, trying to find another way out after seeing the last transports take off without him. After traveling through a zombie-infested 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.
  • Friendly Fire - After battling through an office complex filled with aliens, Shephard comes to a hangar where he sees two soldiers in black combat gear loading a nuclear warhead into the back of a truck. He realizes that the Black Ops soldiers have been sent in 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.
  • We Are Not Alone - Shephard arrives at the Lambda core just in time to see Gordon Freeman teleport to Xen, a scene from the first game. Shephard is also forced to travel through Xen to find a way out of the Lambda core. Upon doing so, he finds the dislocator.
  • Crush Depth - Back in Black Mesa, Shephard arrives in a complex of underwater laboratories where several Ichthyosaurs are being held. After making his way through the labs, Shephard is again forced to teleport to Xen and back again to reach a new part of Black Mesa.
  • Vicarious Reality - Shephard fights his way through a part of Black Mesa featuring massive terrariums used to house Xen fauna being studied by the scientists. Eventually he reaches an older industrial area, and picks up a radio transmission from a group of Marines fighting some kind of massive creature.
  • Pit Worm's Nest - Shephard arrives in an industrial waste-processing area of Black Mesa, where an enormous Pit Worm is blocking his progress. 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 (the sewers of Black Mesa). This chapter is very similar to the Blast Pit chapter from the original Half-Life.
  • Foxtrot Uniform - Accompanied by several fellow Marines, Shephard makes his way through surface areas of Black Mesa controlled by Black Ops forces, including several snipers. He 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 level name references military jargon for "fucked up".
  • "The Package" - Shephard fights his way across the surface areas of Black Mesa, facing down Black Ops troops, artillery, a black AH-64 Apache and alien Shock Troopers. Eventually he comes to an underground parking garage where the thermonuclear warhead from Friendly Fire chapter is being activated by two Black Ops commandos, apparently with the intent of destroying the facility. Shephard kills them and deactivates the nuke, but later sees the G-Man reactivating it.
  • Worlds Collide - After making his way through warehouses filled with Race X creatures and Black Ops soldiers fighting, Shephard arrives at an old industrial area of Black Mesa where an enormous Gene Worm is attempting to come through a portal from Xen. Shephard uses mounted laser weapons to blind and kill it; in its death throes, an enormous teleportation portal spreads outwards and envelops him.
  • Conclusion - 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 Shepard reminds him of himself, but is still a dangerous witness. The G-Man walks into a portal, and the game then ends.

New features

Being an expansion pack, Opposing Force added many new aspects and capabilties to Half-Life's gameplay. It is notable for the introduction of squad-based support. Whereas the player in the original had to rely on composite models of a security guard or scientist, the player in Opposing Force can rely on other soldiers of different classes, including the regular support soldier, a heavy machine-gunner, an engineer, and a medic. Each class possesses unique abilities, such as the engineer being able to cut through certain doors and the medic being able to heal teammates. The AI was improved to allow better coordination of offensive actions during combat.

Opposing Force also included several new weapons. A weapon based on the barnacle creatures acts as a grappling hook. Other organic weapons such as the Spore Launcher and Shock Roach are based on the newly-introduced Race X aliens. In the single-player campaign, some of these weapons replace their old Half-Life counterparts (Desert Eagle - Colt Python, M40A1 - Crossbow, Pipe wrench/Combat knife - Crowbar). However, in the multiplayer game the player can carry both the new Opposing Force weapons and their Half-Life variants at the same time.

Additionally, a new class of security guards was added. Like Barney in the original game, Otis, also named after a character in The Andy Griffith Show, served a similar role. Having the appearance of an overweight and balding guard, Otis can follow the player and provide support during combat. However, Otis is armed with a Desert Eagle, making him much deadlier in firefights than Barney, who is armed with the weaker Glock 17. He also never reloads like the NPC Barney.

Trivia and notes

  • Senior Drill Instructor Dwight T. Barnes (voiced by Jon St. John) who appears in the training section, is modelled after R. Lee Ermey's Gunnery Sergeant Hartman from Stanley Kubrick's Full Metal Jacket. The same drill instructor is also heard to say "You wanna come and knock me off?" when standing on top of a rope climbing platform. This line is said by Sgt. Hulka in the film Stripes during a similar training exercise.
  • To kill the Pit Worm, Shephard must activate the "valve" and "gearbox," an obvious reference to developers Valve Software and Gearbox Software..
  • Two rooms in the Pit Worm level bear a strong resemblance to the garbage crusher in Star Wars, particularly the pattern of red lights above its entry hatch, which varies in number. Also, each trash compactor has an overhead control room; the first showing the G-man, and the second can be accessed, revealing a red button, which closes the doors of the 2nd trash compactor, moves its two walls, and crushes everything, indicating another reference to Star Wars.
  • If the player enters Freeman's Xen portal, the game will end, accusing the player of trying to rewrite history - "Evaluation terminated: Subject attempted to create a temporal paradox." However, If the player uses the "noclip" command from the developer console, he or she can reach an asteroid in Half-Life's exact position where a 3rd-person point-of-view shows Gordon Freeman in his hazard suit wearing sunglasses.
  • In the Boot Camp tutorial, footlockers in the barracks are named after the game's developers. The G-Man also makes an appearance.
  • When the player is first teleported to Xen and gets the Displacer weapon, alt-firing it at that point teleports Adrian to the original Half-Life's Hazard Course's duck-jump section. The player can then observe a Vortigaunt fruitlessly and comically trying to attack the holographic assistant in different ways. An exit portal is located in the room usually occupied by observing scientists.
  • In the chapter "We are Pulling Out," before the player first sees a Shocktrooper, a security guard asks: "Have you seen the new IG-88?" in a possible reference to Star Wars.
  • In one of the rooms a framed picture of Gordon Freeman with the text "employee of the month" written above it hangs on a wall.
  • Near the end of Vicarious Reality, the marine heard by Shephard on the radio says, "we need backup now, now dammit now!". This is a Die Hard line.


The Opposing Force soundtrack, listed below, is credited to Chris Jensen. The soundtrack was subsequently re-ordered and used for the U.S. CD version of Half-Life: Blue Shift, as OpFor was bundled on the same disc.

This is the list of tracks as they appear on the original Opposing Force CD.

  • 1. "Scientific Proof" - 00:15
  • 2. "Orbit" - 00:46
  • 3. "Name" - 01:50
  • 4. "Listen" - 00:15
  • 5. "Fright" - 01:02
  • 6. "Storm" - 01:36
  • 7. "Trample" - 01:16
  • 8. "Bust" - 01:47
  • 9. "The Beginning " - 02:03
  • 10. "Lost in Thought" - 01:19

  • 11. "Danger Rises" - 01:11
  • 12. "Soothing Antagonist" - 01:25
  • 13. "Run" - 00:51
  • 14. "Open the Valve" - 01:22
  • 15. "Tunnel" - 01:24
  • 16. "Chamber" - 01:32
  • 17. "Maze" - 00:57
  • 18. "Alien Forces" - 01:14
  • 19. "Planet" - 01:30

This is the list of tracks as they appear on the Blue Shift CD.

  • 1. "The Beginning " - 02:03
  • 2. "Lost in Thought" - 01:19
  • 3. "Danger Rises" - 01:11
  • 4. "Soothing Antagonist" - 01:25
  • 5. "Run" - 00:51
  • 6. "Open the Valve" - 01:22
  • 7. "Tunnel" - 01:24
  • 8. "Chamber" - 01:32
  • 9. "Maze" - 00:57
  • 10. "Alien Forces" - 01:14

  • 11. "Scientific Proof" - 00:15
  • 12. "Planet" - 01:30
  • 13. "Orbit" - 00:46
  • 14. "Name" - 01:50
  • 15. "Listen" - 00:15
  • 16. "Fright" - 00:06 / 01:02 (See note)
  • 17. "Storm" - 01:36
  • 18. "Trample" - 01:16
  • 19. "Bust" - 01:47

(Note: Track 16 on Blue Shift is apparently "broken", so to speak, perhaps due to a mistake when the game was being burned to the master disc, but corresponds to track 5 on Opposing Force. Track lengths are taken from the Blue Shift CD; the tracks on the OpFor'' disc often include from 2 to 45 seconds of silence on the end.)

See also

External links

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