The Jugurthine War appears in The Social Contract not as a narrated campaign but as the setting for a consequential change in Roman military recruitment. Rousseau identifies Marius’s introduction of freedmen, vagrants, and other mercenaries into the legions as a dishonor to the army, contrasting paid service with the earlier Roman ideal of citizens who gave their lives for their country but would not sell that service. The episode supports his broader argument that a state’s military arrangements can weaken the civic bonds on which its freedom depends.

The War and the Change in Recruitment

Rousseau places the change during the Jugurthine War, after the Roman infantry had already begun receiving pay at the siege of Veii. Under Marius, recruitment widened to include freedmen, vagrants, and others whom Rousseau groups as mercenaries. The text does not recount the war’s battles or identify its opposing commanders; its focus is the institutional consequence of drawing soldiers from this new pool.

The contrast is with the victories of early Rome, and with those of Alexander, which Rousseau attributes to brave citizens prepared to shed their blood for their country but unwilling to sell it. Payment and recruitment thus signify more than a practical adjustment: they mark a shift from civic service toward a military force whose connection to the country rests on employment rather than citizenship.

Mercenaries, Rulers, and the Citizens

Rousseau links the growth of paid forces to a danger in the relation between government and the people. When citizens cease to feel invested in the common cause, they may no longer defend their country themselves; magistrates can then prefer mercenaries to free citizens, in part because troops may be used to bring those citizens into submission. The army’s change is therefore presented as a political risk, not simply a response to military needs.

This argument belongs to Rousseau’s wider account of the conflict between government’s particular will and the general will. As government presses against the sovereignty of the people, the constitution changes and the political compact is threatened. The mercenary army supplies a concrete historical example of how rulers’ instruments of power may become detached from the citizens whose common interest the state is meant to serve.

Consequences and Historical Significance

Rousseau’s surrounding account traces the costs of maintaining regular troops: taking men from the land diminishes agricultural labor and provisions; maintaining the army requires taxes that raise prices; public discontent follows, and suppression of that discontent demands still more troops. He presents this as a self-reinforcing cycle in which the measures meant to secure government deepen popular hardship.

He places this development in a longer Roman decline, describing regular troops under tyrants as ostensibly directed against foreign enemies but in practice capable of enslaving their fellow citizens. The Jugurthine War is consequently a landmark in his argument about the corruption of military service: Marius’s recruitment is associated with the erosion of the citizen army, while the later use of mercenaries helps explain how armed force could be turned inward and become one of the principal causes of the Roman Empire’s ruin.