There are many ways to categorize armies, but the most representative is dividing them into four major types: classical armies, mercenary armies, modern armies, and contemporary armies.
The backbone of classical armies was the citizen-soldier—for example, the fierce soldiers of the Qin, the Northern Dynasties' government troops, even Sparta, Macedonia, and Rome (in the republican era)—all can be considered classical armies. Their soldiers were citizens, freemen (during the era of slavery), or small landlords and self-sustaining farmers (under feudalism). Soldiers occupied a relatively high social status, usually trained of their own accord, joined voluntarily, and tended to have strong fighting spirit.
The internal driving force behind these classical armies was the sense of personal honor and the hope of raising one's social standing; as the classical era ended, it became nearly impossible to replicate this.
