The governmental structure of the Greek city-state of Sparta was unique among the major Greek poleis because it maintained an inherited diarchy, meaning it had two simultaneous kings. These kings represented two distinct royal houses: the Agiads and the Eurypontids.
Mythological Origins and Dynasties
According to Spartan tradition, the two dynasties traced their lineage back to the legendary hero Heracles. The foundation myth states that the system began with the twin descendants of Heracles, Eurysthenes and Procles, who conquered Sparta a few generations after the Trojan War.
The Agiads dynasty was named after Eurysthenes' son, Agis. This line was considered the senior or elder house.
The Eurypontids dynasty was named after Procles' grandson, Eurypon.
This mythological explanation provided a powerful, divinely sanctioned justification for the highly unusual dual-kingship.
The Practical Function of Diarchy
While the mythical origin explains who the kings were, the system persisted for practical political reasons:
Checking Power: The main historical benefit was mutual restraint. Each king served as a check on the power and ambition of the other. If one king attempted to overreach, the other king—who belonged to a rival dynasty—had the authority and political incentive to challenge him.
Military Expeditions: In times of war, Sparta traditionally sent out only one king to lead the army on campaign. This ensured that a king was always present in Sparta to maintain order, handle domestic affairs, and manage the legislative body.
Judicial and Religious Duties: The kings also held crucial roles as the chief priests (responsible for sacrifices and state religious affairs) and as the supreme judicial authority in certain matters.
Kingship within the Spartan Constitution
The two kings were not absolute monarchs. Their power was heavily constrained by other elements of the Spartan political system, which included:
The Gerousia (Council of Elders), composed of the two kings and 28 elderly Spartan nobles, who prepared legislation.
The Ephors (Overseers), a board of five annually elected magistrates who held true political power. The Ephors could veto the kings, convene the assembly, and even impeach and prosecute a king.
This system, sometimes called a mixed constitution, meant that the two kings essentially served as a permanent, sacred executive and military leadership, subject to the control of the Ephors.
Examples of Spartan Kings
The diarchy produced many famous leaders:
Agiad Cleomenes I (c. 520–490 BC) - Known for interventionist policies in the Peloponnese and Athens.
Agiad Leonidas I (c. 490–480 BC) - Led the small force of Spartans at the Battle of Thermopylae (480 BC).
Eurypontid Demaratus (c. 515–491 BC) - Famous for his rivalry with Cleomenes I, leading to his exile.
Eurypontid Agesilaus II (c. 400–360 BC) - A highly successful military leader who dominated Greek affairs after the Peloponnesian War.
While the Spartan diarchy was unique in classical Greece, other forms of diarchy existed in the ancient Mediterranean, such as the two annually elected Suffetes (or shophetim) of Carthage and the two annually elected Consuls of the Roman Republic.
