Warzone 2100

Warzone 2100 is a real-time strategy game in a post-apocalyptic setting that was developed by Pumpkin Studios in 1999. It was one of the first real-time strategy games in 3D, and is now the first commercial RTS that was made available under the GPL in December 2004.
"The Collapse came fast and hard. Following a technical error in the satellite defense system nuclear warheads were fired at Washington, Beijing and Moscow. Minutes later ground based sites fired in response to the launch. Millions died as nuclear firestorms wiped out the world's cities. Billions more died as plagues and epidemics swept away what remained of civilization. Less than a million people survived the Collapse. Earth broke into hundreds of small scavenger bands battling each other for the remnants of he former civilization. Only a few had the vision to attempt to rebuild a new world from the ashes."