In the second game , Half-Life 2 , Gordon is introduced to a miltary world years after the Black Mesa incident , along with a force known as the Combine that took over the world . In its sequel , Half-Life 2 , Gordon is introduced to a dystopian world years after the Black Mesa incident , along with an interdimensional imperial force known as the Combine that took advantage of the interdimensional portals and has established itself as the ruling force on Earth .