[throwaway8582]

> Agricultural societies can subjugate conquered lands so much faster than hunter gatherer and nomadic peoples.

Nomadic people are quite capable of conquering land, the most obvious example being Genghis Khan, who managed to build the Mongol empire into the largest in human history.

It is true there is a general trend in history of agricultural societies displacing hunter/gather societies, but that's simply because agriculture generates more calories per square kilometer than a hunter/gatherer lifestyle. As populations grow beyond the carrying capacity of the natural environment, hunter/gatherers either forced to adopt agriculture or get conquered by the larger armies of those people that have.