They began development in September 2007, one month before the release of Half-Life 2: Episode Two. The Valve Corporation originally had plans to port Half-Life: Opposing Force into the Source engine (announced at E3 2004) much like they did with Half-Life: Source, but after an underwhelming first look at the project, the creators of Operation: Black Mesa decided to pursue their own remaster of the game, built from the ground up.
