In January of 1904, the Herero rebelled against German colonists, who had pushed the tribesmen off their land and taken much of their cattle. Germany responded with swift, sweeping military force intent on "wiping out" the rebellious tribe. The German troops forced the Herero into the unforgiving Kalahari Desert, poisoned the few water holes there, rounded up any who survived disease and starvation in the desert and placed them in work camps where they were kept as labor and sex slaves by German settlers. 80% of the Herero population was killed in the German campaign, the first genocide of the twentieth century.