Half-Life 2: Wars is a Realtime Strategy modification in the hl2 universum. The mod is has most basic features you would exspect from a rts game, including unit control, objectives, mission structure, rts navigation and a fog of war. To gain resources, there are points that can be captured, and generate a slow income. Mapping documentation is also available on the forum.
Base building is not possible yet, but will follow in the next release. Same for fully worked out sides and multiplayer.