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Half-Life: Opposing Force

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Title Screen

Half-Life: Opposing Force

Developers: Gearbox Software, Valve
Publisher: Sierra Studios
Platforms: Windows, Mac OS X, Linux
Released in US: November 18, 1999
Released in EU: November 29, 1999

AnimationsIcon.png This game has unused animations.
DevMessageIcon.png This game has a hidden developer message.
CopyrightIcon.png This game has hidden developer credits.
GraphicsIcon.png This game has unused graphics.
ModelsIcon.png This game has unused models.
ItemsIcon.png This game has unused items.
SoundIcon.png This game has unused sounds.
TextIcon.png This game has unused text.
RegionIcon.png This game has regional differences.
Carts.png This game has revisional differences.

ProtoIcon.png This game has a prototype article

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Half-Life: Opposing Force is an expansion to Half-Life. You are Adrian Shephard, one of the soldiers sent to "silence" Black Mesa's staff. However, your transport plane is shot out of the air before you can land, and you awaken soon before the military pulls out. Trapped with stranded fellow soldiers and what remains of Black Mesa's staff, you must escape the facility while fighting off against the Black Ops seen in the first game (now augmented with male troopers as backup) and the mysterious Race X. Thankfully, you have the power of friendship a lot of powerful new weapons to help deal with the new foes.


Read about prototype versions of this game that have been released or dumped.
Prototype Info

Unused Models

Black Ops Osprey

Hlop4 blops osprey 1.png

The Black Ops were to have their own V-22 Osprey at one point. It was cut, but the model for it is still in the game.

It also has its own unique gib models.

Destroyed Black Ops Osprey

Hlop4 blops dead osprey 1.png

The Black Ops Osprey also has a "dead" variant that is also unused. It looks the same as the "dead osprey" model that appears throughout the game, but with the Black Ops coloring on it.

Dead Gordon Freeman

Hlop4 deadgordon.png

The model deadhaz.mdl contains an unused variant with Gordon's head instead of the generic HEV Suit helmet.

Unused Weapons

Flash Grenade

Hlop4 flashgrenade.png

An item model for an unused Flash Grenade can be found in the game's files. The same flash grenade, albeit low detailed, can be found carried by Black Ops assassins.
This and the lack of a first person model could mean that these flash grenades were supposed to be a monster-only weapon used by the Black Ops assassins alongside frag grenades to further hinder the player.

Single Player .357 Magnum Revolver

Hlop4 357revolver.png

While the .357 Magnum Revolver can be found in multiplayer mode, the player can only see its multiplayer version. The single player version (without the laser sight) can't be seen without cheats because it does not appear in the single player campaign.

Suppressed Pistol

Hlop4 suppressor.png

The suppressor for the Pistol is still in the game, but some changes to the weapon's model have made it so that the suppressor floats underneath where the barrel is instead of being attached to it. The "add_silencer" animation is still there as well and has the same problem.

Unused Animations

Drill Instructor

The Drill Instructor has a few unused animations.

  • bino_look: The Drill Instructor takes out a pair of binoculars (which can be found and added to his model) and looks through them.
  • blow_whistle: The Drill Instructor takes out a whistle and blows on it. The whistle is in his model file and can be made so that he holds it.
  • mega_yell: The Drill Instructor takes out a megaphone and begins yelling into it.
  • mega_blow: A looped animation of the Drill Instructor yelling into a megaphone.


The Gonome has two unused animations.

  • jump: The Gonome jumping.
  • sohappy: An animation of the Gonome doing a silly dance where he claps while moving his body around. Named "veryhappy" in the WON version of the game.

Hazmat Scientist

The Hazmat scientist contains all of the animations the Opposing Force Scientist has, but he doesn't use a majority of them.

Human Grunt Zombie

The Human Grunt Zombie has an animation of it getting up from its stomach.


The Knife has two unused animations.

  • Charge: An animation showing Shepard pulling the knife back. Based on its name, it seems that the knife could be charged to do more damage, like with the Pipe Wrench.
  • Stab: Adrian stabs with the knife. Seems to be related to the previous animation.

Laser Trip Mine

The Laser Trip Mine's first person model still has the "arm1" animation that was unused in the original game as well.

Otis Security Guard

The Otis-type Security Guard contains several unused animations from the original Half-Life Security Guard, such as "stuffed_in_vent".

Security Guard Zombie

The Security Guard Zombie has all of the animations from the original Zombie. Quite a few of these are not used.

Half-Life's Human Grunts

The Human Grunts from the original Half-Life are still in the game and can be summoned with the cheat "impulse 76". Gearbox Software wisely decided against editing the original grunts from Half-Life as doing so would break original fan-made maps that feature them as enemies. Instead, a separate ally grunt entity was made using the Half-Life grunt model early in development before transitioning to new models made by Gearbox.

When spawned, they will attack friendly soldier NPCs but not Black Ops assassins because both use the same relationship table (code that handles how entities treat each other).

Unused Map content

Boot Camp signature


In the first Boot Camp level (ofboot0), there is a signature by the mapper David Michael Mertz of Gearbox with the year of creation. It's only accessible by using noclip to get past two locked doors.

Half-Life's Xen

If the player follows Gordon through the portal at the start of We Are Not Alone, they will be teleported into the chapter Xen from the original game, but will fall into the void. However, with noclip, the level can be played, and a surprising amount of it is playable.

Since the player lacks the Long Jump Module, cheat codes are required to spawn it in (or the use of Noclip to fly straight to the center asteroid). With it, the player can trigger all of the assaults on the way to the main asteroid from the asteroid Gordon is on, reach the main asteroid, then kill all of the Houndeyes that roam the area and all of the items around the asteroid's perimeter (such as the Medkits). However, the ways to the center of the asteroid are blocked. Using noclip to see the core of the asteroid will reveal that the level designers stripped out everything inside it, making it impossible to activate the teleporter.

Of note is that the laser-shooting objects around the perimeter do not shoot lasers and cannot be destroyed.

Multiplayer level signatures

Hlop4 bootcampsig.png

Opposing Force's version of Boot Camp still has Dario Casali's signature, as seen in the original version of the level.

Unused Sounds

The file "sound/sentences.txt" contains a list of sentences allowing the game to easily call a sound, or string of sounds, for these purposes. This section includes both unused sentences and unused sound files without an associated sentence.

Barney Security Guard

Sound Name Transcript
die I don't wanna die!
killme No, don't kill me!


Sound Name Sentence Transcript
SC_BETTERLUCK scientist/of1a1_sc04 I'm afraid these troops aren't going to make it. I hope you have better luck out there, or I fear none of us will get through this alive.

Scientist-Security Conversations

Multiple unused lines for a scene in We Are Not Alone, involving a Displacer cannon teleport mishap between a Scientist and an Otis guard.

Sound Name Sentence Transcript
OT_TRANSPORTER otis/of3a2_ot01 Huh! What's this? Some sort of transporter gun?
SC_PUTDOWN scientist/of3a2_sc01 Put that thing down! Why must you security guards always insist on playing with our prototypes.
SC_NOTAGAIN scientist/of3a2_sc02 Be careful. No, not again!

Otis Security Guard

Sound Name Sentence Transcript
OT_FINDMORE otis/of1a1_ot04 Personally, I think if we could find more soldiers like you, we may come out of this a-okay.
OT_TRUSTYA otis/of2a6_ot01 I'm not sure I can trust you, but I don't know what else to do at this point. If you make it out of here, don't forget me.

Human Grunts

Sound Name Sentence Transcript
FG_WIPEDOUT fgrunt/of3a4_fg01 Don't go in there, Corporal. That... monster... wiped out my squad!
FG_TABLES fgrunt/of5a1_fg03 Yeah, I'd love to turn the tables on those guys. Get my hands on one of those rifles, show them a thing or two about patience.
FG_SUPRISE fgrunt/of5a1_fg04 Hey, with you here now we have the element of surprise on our side. They're not expecting three of us. Heh heh heh.
FG_EVAC fgrunt/of5a3_fg01 Shephard! Oh man, we thought you made evac already!
FG_FIREPOWER fgrunt/of5a3_fg03 We may just have enough fire power to push through now. The very least, we can give it our best shot.


Sound Name Sentence Transcript
INTRO_FG4_L2 fgrunt/intro_FG19 What the hell kind of mission is this, anyway? We didn't even get a briefing before take-off.
300px INTRO_FG4_L1 fgrunt/intro_FG18 Hey, you sleeping over there? You want me to fluff your pillow for ya?


Sound Name Sentence Transcript
RD_RALLYPOINT radio/of1a6_rd01 All units, retreat to the rally point. I say, retreat to the rally point. (Medic!) Orders have been changed. We are pulling out. The safety of any units left behind cannot be guaranteed.

Military Police

Sound Name Transcript
athority [sic] Don't confuse your rank with my authority, Corporal.


Sound Name Transcript
sirtexas Sir, Texas, sir!
sirnosir Sir, no, sir!

Drill Instructor

Different voice takes are used for common interaction quotes.

Sound Clip File Name Transcription
DR_ADD01 drill/add01 You eyeballin' me, boy?
DR_ADD02 drill/add02 Are you touchin' me, dirtbag?
DR_ADD03 drill/add03 What is your major malfunction?
DR_ADD04 drill/add04 It's time to kick ass and chew bubble gum, and I'm all out of bubble gum!
DR_ADD05 drill/add05 I eat concertina wire and piss napalm!
DR_ADD06 drill/add06 God has a hard-on for Marines.
DR_ADD07 drill/add07 I eat Green Berets for breakfast!
DR_ADD08 drill/add08 You had best get your head on straight, maggot!
DR_ADD09 drill/add09 Soldier, you are all ate up!
DR_ADD10 drill/add10 Son, I will break you down like an M16!
DR_ADD11 drill/add11 I smell smoke! And where there's smoke, there's fire! You better move it, soldier!
DR_ADD12 drill/add12 I will smoke you like a Cuban cigar!
DR_ADD13 drill/add13 Drop and give me twenty, maggot!
DR_ADD14 drill/add14 Get down and break them elbows!
DR_ADD15 drill/add15 What's your first general order, dirtbag?
DR_ADD16 drill/add16 Where you from, soldier? Texas! Holy cow! You know what comes from Texas, don't you?
DR_ADD17 drill/add17 Can I be in charge around here? Well, thank you very much!
DR_ADD18 drill/add18 You had better square yourself away, Marine!
DR_ADD19 drill/add19 You better move like you've got a purpose!
DR_BARRACKS08 drill/barracks08 One! Two! Three! Four! I! Love! The Marine! Corp!
DR_SOUND4 drill/sound4 What is your major malfunction?


Sound Name Notes
old_reveille An old reveille sound file which was cut from the final game. This version of the reveille horn is a little duller, and doesn't have as much reverb as the one in-game.

Gene Worm

Inside of "sound/misc/" is a sound related to the Gene Worm named "dsbossit.wav", which when played backwards, is a rendition of Gearbox CEO, Randy Pitchford, saying "To win the game, you must kill me, Randall Pitchford." in a similar manner to Doom II.

(Source: MonsieurNuby)

Unused Graphics


The files contain three sprite series called "comp". The first one, called comp_a, shows one of the servers from the original game's Apprehension, with and without a hole in it (which can happen in the level the server appears in). Comp_b is a smaller version of comp_a. Comp_C shows a traditional 90s desktop computer with two variants. The first variant has a hole in the monitor and jagged bubble surrounding it, while the second one has the damaged computer from the first variant with a No sign over it.

The graphics have the correct colors needed to be on the HUD.

Nuclear Explosion

Three graphics for a small nuclear explosion are in the game's files. Two of them are the same, while the third one has a transparent background.

While a nuclear explosion does happen at the end of the game, the player is never able to see the explosion itself.

Won logo.png

In WON versions of Opposing Force, in the pak0.pak folder "gfx\shell" there is a graphic called "won_logo.bmp".

Unused Sprites

There are two unused sprite sets with the name "sprite". The first one is a literal sprite, while the second one is an orb with a large star-like shape in the center of it, similar to the floating orbs seen in the last scene of the game.

Happy Face

Hlop4 happyface.png

The unused happy face from the original game's HUD files makes a reappearance in Opposing Force.

Hidden Hack Texture

OP4 Hackup.png

If the player uses console commands 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:



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's files.

CTF HUD Graphics Message

Hlop4 ctf message.png

The graphics for the HUD icons in CTF mode have "Opposing Force Capture The Flag" crudely doodled at the bottom of them. This message is never shown in-game.

Unused Text

Disabled Developer Credit

Within titles.txt, there's an additional developer name among the names displayed during the intro. It's aditionally mentioned inside the map logic of the intro, but is not timed correctly to be displayed.

Tollbooth Willy

This also happens to be a reference to Adam Sandler's song, Toll Booth Willie.

(Source: Marphy Black)


Gearbox originally created three pak files for the game's content. For whatever reason, one of them (pak0.pak) contains a file called, "placeholder.txt":


The pak files were removed in the SteamPipe update, meaning they can only be found in the retail release.

Developer Configuration Files

In the CD release, there exists configuration files from Opposing Force developers that make references to unused maps and hidden console commands. These files can be found in "pak0.pak".

bind "F2" "map of1a3"
bind "F3" "playdemo ectsdemo1"
bind "F4" "map of2a5dmo"
bind "F5" "playdemo ectsdemo2"

Hidden Console Commands

There are some hidden console commands in Opposing Force.


By typing "haiku" into the console on any map, a haiku will be written across the screen. The way it works is that it takes several random sentences and botches them together to form a unique haiku every time.

A complete list of phrases is provided at Half-Life: Opposing Force/Haikus.

Impulse 99

This command (which is also in Half-Life) displays several company logos and the game title in the upper right corner. Only used for pre-release videos and screenshots, it was modified by Gearbox for Opposing Force. The only difference from Half-Life is the addition of the Gearbox and Half-Life: Opposing Force logo. This was used during E3 1999 during some gameplay footages.

This command will not function at resolutions above 1024x768.

Revisional Differences

Main Menu

The main menu's layout underwent the same changes that the original game did, which removed the unique descriptions for the main options and the little animated "Opposing Force" logo that had soldiers and an Osprey going through a desert in it.

The background graphic is mostly the same, but the Steam version replaces the lambda logo with an image of Adrian holding a green flag and Gordon holding another flag to show off the CTF mode.

Pre-Steam versions Current Steam release
Hlop4 won menu.png Hlop4 steam menu.png


And like the base game, the console was changed to dropping down when activated to having its own window.

Pre-Steam versions Current Steam release
Hlop4 won console.png Hlop4 steam console.png