Warfare in Hellenic Greece centered mainly around heavy infantrymen called hoplites. These were a citizen-militia, and so were armed as spearmen, which are relatively easy to equip and maintain; mainly they represented the middle class, who could afford the cost of the armaments. Almost all the famous men of ancient Greece, even the philosophers and playwrights, fought as a hoplite in some battle or another.
Since farming was generally at the subsistence level, campaigns were short and mainly confined to the summer. Armies marched directly to their target. There the defenders could hide behind city walls, in which case the attackers generally had to content themselves with ravaging the countryside as siegecraft was undeveloped, or meet them on the field. Battles were usually set piece and intended to be decisive. Both forces lined up on a level field, usually in a rough phalanx around eight ranks deep (though this varied). Other troops were less important; cavalry generally protected the flanks, when present at all, and both light infantry and missile troops were negligible.
Hoplites generally armed themselves immediately before battle, since the equipment was so heavy. Each man provided his own gear so it was fairly non-uniform, and often friendly troops would fail to recognise one another. A hoplite typically had a breastplate, a bronze helmet with cheekplates, as well greaves and other armor, plus a bowl-shaped wooden shield around 1 metre across. The primary weapon was a spear, around 2.7 metres in length; as this frequently broke upon charging, hoplites also carried a smaller 60 cm thrusting sword.
By contrast, other contemporary infantry tended to wear relatively light armor, and was armed with shorter spears, javelins, or bows. Shields were usually smaller, or else were large enough to cover the full body and rested on the ground. The middle-sized shield of the hoplite was made possible in part by the shape, which allowed it to be supported on the shoulder. In formation the shields were locked together so that each defended the left side of the soldier carrying it and the right side of his neighbor, while the spears were gripped overhand and thrusted down at the opponents.
The strength of hoplites was in shock combat. The two armies would literally run into each other in hopes of breaking or encircling the enemy line. Failing that, things degenerated into a pushing match, with the men in back trying to force the front lines through those of the enemy. Battles rarely lasted more than an hour or so. Once one of the lines broke, the troops would generally drop their equipment and flee from the field, generally unpursued. Casualties were slight compared to later battles, rarely amounting to more than 5% of the losing side, but the slain often included the most influential citizens and generals who led from the front. Thus the whole war was usually decided by a single field battle; victory was enforced by ransoming the fallen back to the defeated, called the "custom of the Greeks" in contrast to the oriental practice of mutilating the slain.
The rise and fall of hoplite warfare was intimately connected to the rise and fall of the city-state. Its practice began to decline during the Peloponnesian War, when there were three major hoplite battles, none of which decided anything. Instead there was increased reliance on navies, skirmishers, mercenaries, city walls, siege engines, and non-set piece tactics. These reforms made wars of attrition possible and greatly increased the casualties of battle. Many of them were combined by the brilliant general Epaminondas, whose tactics formed the basis for the Macedonian phalanx of Philip II of Macedon, used as a back-up to his cavalry. These forces defeated the last major hoplite army, even then fairly reactionary, at the Battle of Charonea, after which Greece became part of the Macedonian empire.
Hoplite-style warfare was also practiced around the Mediterranean basin. Of particular note, the Etruscans usually fought with such militias, a practice they adopted from the Greek colonies. From this sort of warfare developed the Roman legion that was to dominate western military history for hundreds of years.