Putting people in cities is a great way to kill off as many as you need to in order to “right-size” the population to the world. You just cut off roads going out and go through the city in a grid-like fashion and kill all that are deemed unworthy.
According to the mysteriously demolished “Georgia Guidestones”, the right size human population is 500,000,000.
That means killing 94% of the current human population.
“Genocide” doesn’t even properly describe it ...