chunk: The Oligarchy are the largest monopoly trusts (or robber barons) who manage to squeeze out the middle class by bankrupting most small to mid-sized business as well as reducing all farmers to effective serfdom. This Oligarchy maintains power through a "labor caste" and the Mercenaries. Labor in essential industries like steel and rail are elevated and given decent wages, housing, and education. Indeed, the tragic turn in the novel (and Jack London's core warning to his contemporaries) is the treachery of these favored unions which break with the other unions and side with the Oligarchy. Further, a second, military caste is formed: the Mercenaries. The Mercenaries are officially the army of the US but are in fact in the employ of the Oligarchs.