The military reputation of ancient Sparta was so intense and well-known that, as one saying went, the men were the walls. For a time, Sparta was unique in the Greek world in not having a city wall; the story goes that the city didn't need a physical wall because the fighting prowess of the Spartan warriors was enough.

Spartan culture, from very early on in both the life of the city-state and the lives of its people, was all about discipline and athleticism and war. Athletic competitions were many, and winners were highly celebrated. Athletic and military training went hand-in-hand. The fighting was for boys only; strong, athletic girls were seen as potential mothers of the next generation of strong, athletic (male) warriors. One widely told story about ancient Sparta is that newborns found to be deficient in mind or body were tossed off a cliff, into a chasm on Mount Taygetos.

Boys and girls both were expected to be prime specimens of physical fitness. Competitions were of great importance and of great regularity. Young people of both genders were expected to be good at running, wrestling, throwing the discus and the javelin, and horse riding and racing.

Boys left their homes at age 7 and headed off to (military) boarding school, where they learned to be hard-fighting soldiers. Greek tradition speaks of a training system known as the agōgē, which involved not only military training and hunting but also more cultural pursuits such as dancing and singing and, perhaps, some academic instruction. Despite the inclusion of these cultural elements, though, the agōgē was first and foremost a series of exercises in discipline. Boys were often underfed, so as to be accustomed to such conditions if they occurred while soldiers were on campaign (or involved in a daylong battle).

Boarding school lasted a dozen or so years for most recruits; the next step was life in the barracks. Even soldiers who married were expected to live in the barracks. Military service was compulsory for men aged 20 to 40; from there, for the next 20 years, it was a reprieve to being placed on reserve duty. When Sparta needed the most fighting men, it called on men as old as 65.

Sparta's dominance of Messenia notwithstanding, Sparta did not immediately become a world-beating power. The very next fight Sparta picked with another city-state went not the way of Sparta. Argos it was that defeated Sparta in battle, in large part because of a new battle formation called the phalanx, a combination of spears, shields, and tightly formed marching and fighting soldiers that proved very nearly invincible for generations of Greeks and particularly for the Macedonia-led armies of Philip II and Alexander the Great.

Sparta did not invent the phalanx; Sparta vastly improved the phalanx. The Sparta-infused phalanx presented a shield wall, wherein each warrior held his shield in his left and overlapped his own left side and the right side of the soldier to the left of him. Soldiers held spears in their right hand, and the spear points poked through small gaps in the shield wall, which would close up again in defense. A line of soldier directly behind a shield wall would wield much longer spears, which could augment the front line spear attacks; alternately, the front line could be a shield wall only, allowing the second line longer spear attacks to reap maximum effect.

A Spartan in battle typically wielded a spear and a sword. The spear was known as the doru or dory, which had a leaf-shaped spearhead on the end pointed toward the enemy, and a spike on the end held close to the warrior. The sword was a short sword, with two types: xiphos and kopis. A xiphos sword was leaf-shaped; a kopis was a curved blade, known as a xiphos and was of the short sword variety, generally about two feet long. Spartan soldiers would whip out a sword if the spear were broken or the press of the battle rendered the spear less effective.

Spartan warriors also typically carried a wood and bronze shield, called a hoplon. The hoplon weighed about 30 pounds and, in a pinch, could be used as a weapon in its own right. Many soldiers had the Greek letter lambda emblazoned on the hoplon, honor of their homeland. One story, quoted widely to reinforce the idea of Sparta's military culture, is that soldiers were told by their mothers to return home from battle with the shield or on it (meaning having died a hero, in battle).

Spartan armor usually consisted of a breastplate, helmet, greaves, and sometimes shin armor. This was for the warrior whose family could afford it, of course. Weapons, armor, and shields that continued to be in good condition were passed down from father to son, brother to brother.

Sparta used this training, these weapons, and this strategy to great effect, securing several great victories over other city-states and several legendary victories over foreign powers. Sparta it was that ultimately proved the stronger in the Peloponnesian War, defeating Athens and its allies. Before that, however, Sparta it also was that took a leading role in winning the Greco-Persian Wars, holding back a horde at Thermopylae and leading a coalition to final victory at Plataea.

Spartan military history did not exactly end in victory, however. The long Peloponnesian War weakened Sparta as well. Just over a decade after the end of that war, Sparta became embroiled in another one, the Corinthian War, and fought against Thebes, aided by Argos, Corinth, and a ghost of a force from Athens. Spartan helots revolted during this struggle, distracting the Spartan army when it could least afford it, and Sparta lost up to 4,000 hoplites in a defeat at the hands of Thebes, at the Battle of Lauctra, in 371 B.C. The defeat was sharpened by Thebes' liberating the Messenian helots.

Neither Philip II nor Alexander tried to conquer Sparta. As with so many early civilizations, however, Rome succeeded where others failed. After allying with Sparta against Carthage in the Punic Wars, Rome turned itself to conquest of its former allies, and Roman troops under the general Lucius Mummius conquered Sparta in 146 B.C.