Resistance (Half Life)

The Resistance is a covert network of humans and alien slaves in the Half-Life Universe with the goal of defeating the Combine and restoring freedom to Earth after an attack by the Combine left the Earth's species almost extinct and its natural resources depleted.

Humanity readily uses stolen Combine technology and weapons in order to defeat them at their own game. The enslaved aliens called the Vortigaunts are intelligent and well-versed in combat and prove an asset to the Resistance.