Half-Life: Opposing Force is an expansion pack for Valve Software's science fiction first-person shooter video game Half-Life. The game was developed by Gearbox Software and Valve Corporation and published by Sierra Entertainment on November 1, 1999. Opposing Force is the first expansion for Half-Life and was first announced in April 1999.
I've owned and played this one since it was released alongside TFC and Counter-Strike, back in the early pre-Steam days of the franchise. I have already taken a look at both of those franchises prior to this one, since neither of them were linked to the main Half-Life storyline, and had nothing in common with it besides using the game engine.
Opposing Force centers around a character connected to and parallel to Gordon Freeman: Adrian Shephard, a US Marine Corporal who first arrives at Black Mesa in a combat helicopter, one of several deployed, brimming with Marines fresh from boot camp and ready for a fight, but without being told what they were supposed to be doing there... And before the orders can be given, beyond it being an extremely hostile situation... You guessed it. It goes very bad. Flashes of soldiers being attacked by aliens and dying... A crashed helicopter and bodies... And Shephard regains consciousness next to the bodies of two Marines that were joking and chattering minutes earlier, now bloodied and dead, with a scientist in a lab coat trying to give one of them CPR, without success.
Shephard, as it is later revealed, is one of the team sent to Black Mesa specifically to deal with Gordon Freeman personally, for reasons that were never revealed. Like many of the various soldiers and operatives sent in with this same mission - Shephard finds himself in a largely underground complex trying to keep himself and the other Marines he meets alive long enough to escape from the alien invasion that has made the goateed man in the orange hazard suit a comparatively minor priority.
Over the course of his journey, Shephard actually finds something that was not seen again until the rise of Half-Life 2 - followers. An engineer that could cut open sealed doors, a medic that could heal him or other Marines that were part of Shephard's squad, and a couple of more basic combat types, one carrying a machine gun, and another a shotgun, and so on. The scripting for followers in OpFor is far from perfect, and you find yourself going back frequently, because they tend to get hung up on anything, corners, stairs, even an inch high. Annoying. The AI script also has you sending these enthusiastic sheep tumbling into each others way during a firefight, and into yours as well, which led in one case to two of the four I had found shooting each other, one shooting me, and the last stuck inside a small room. Great. Heavily armored sheep with the brains of decapitated chickens!
You find an eclectic mix of equipment - more organic than any of the others in the franchise that I've seen, from a large barnacle creature that can chew its way through enemies and manage to actually act like a Batrope of sorts. And there's an alien grenade launcher that eats and is powered by... glowing tennis balls. Add a small creature that throws bolts of lightning, and a larger selection of military hardware, and one strange weapon that uses a strange sort of radioactive ammo - I like to call it the Go Away Gun. Tends to turn enemies in the small blast radius into splatters of goo on impact.
You wind up finding a course very parallel as I said earlier - down to having to avoid following Freeman through an extra-dimensional aperture, or it divides the universe by zero and you have to load from your save. In the end, Shephard finds himself in the hands of the G-Man, just as Freeman did. He is not given any choice at all, so instead of being hired, he is simply detained - and as far as I can tell, never mentioned again.