The Greek innovation to ancient warfare was their hoplite warrior phalanx, a formation eight to ten rows of a hundred or more warriors, sometimes extending a quarter of a mile. The shields of the front row would interlock, and the entire formation would press upon the enemy, the soldiers would first throw their spears then jab with their swords from behind their shields, strictly maintaining their position. This required training and practice, the Athenians expected their nobles to drill during the year, the Spartans had a year-round military the practiced year-round.
These Greek hoplite phalanxes were terrifying to encounter on the battlefield. In the first Persian War the Athenian phalanxes approached the Persian forces at a run, shouting war hoops, the Persian mercenaries were not quite used to this élan, they panicked and were slaughtered as they ran. In the second Persian War the three hundred Spartan hoplites held off the entire Persian army in the famous battle at the Pass of Thermopylae.
Before the battle the Spartans were seen brushing their long braids. The Persian king asked his Greek military advisor why they would do this, and he responded that is always what Spartans do before they know they will face death in battle. Spartan women would admonish their sons to either return as heroes or dead on their shields. Herodotus relates that when a Spartan was told that the Persian army was so numerous that when they fired their arrows they would blot out the sun. The Spartans responded that this was good, it meant they could fight in the shade.
Many times hoplite armies parried in a stand-off with no winners. Usually battles were only an hour, some sources estimate that typically there was five percent casualty rate for winners and three times these casualties for the losing side, though other sources suggest that in particularly brutal battles the losing side could suffer horrendous casualties if they broke and ran and were slaughtered by the opposing army.
The well-off noble citizens of ancient Greece were expected to purchase their hoplite equipment. This included a round leather shield covered in bronze, a bronze helmet and breastplate, greaves or shin armor, an eight-foot long thrusting spear, and a short sword.
Most Greek cities had only the infantry hoplites, they had no cavalry forces because horses were not that effective when fighting in mountainous Greece. Later King Phillip and his son Alexander the Great of Macedon would improve upon the Greek military formations by equipping his hoplite soldiers with fifteen foot long spears and adding cavalry units of archers and swordsmen, or other units that took advantage of military skills of his non-Greek subjects.
The Athenian Empire was an ancient Mediterranean version of the British Empire. Athens was a naval power with extensive trading network from Egypt to the shores of the Black Sea, and they had a large fleet of several hundred triremes that defeated the Persian navy. These triremes had three files of rowers, about 170 in total, carrying a small contingent of archers and hoplites. Triremes were fast ships that had a bronze battering ram below the waterline at the font of the ship that was used to sink the opposing ship. Triremes were like huge rowboats, they had to beach overnight and at mealtime, rarely did they attempt to cross the Mediterranean.
The rowers were citizens who usually were not property owners, they were a full-time professional navy paid by the state. It took a great deal of skill and stamina to row these triremes, the crews drilled year-round. These sailors were participants in the democracy of Athens, then as now veterans demanded that their voices be heard by the government.
ROMAN INNOVATIONS OF WARFARE
Like Alexander the Great, the Romans fielded professional armies that could fight for years at a time in distant theaters of war. Alexander’s Greek army and the later Roman army intermarried with the locals and recruited foreign soldiers. Under the Roman Emperor Octavian, the army started to recruit volunteers into the army as professional soldier that would enlist for many years. By the end of first century volunteers outnumbered conscripts in the Roman army, probably one in five of Roman citizens were conscripts in the army. Non-citizens could enlist as auxiliaries that were promised citizenship at the end of their service, adding cultural diversity to the army. When soldiers were injured or had served for twenty-five years they were retired on farms in the provinces, sometimes receiving a stipend, which helped to integrate the empire.
Garland tells us, “the conditions of service in the Roman army were sometimes appalling. According to Tacitus, some men served for 30 to 40 years, ‘their bodies maimed by wounds.’ When they were finally discharged, they might be given ‘a waterlogged marsh or unplowed hillside’ to farm.”
One of the fatal weaknesses of the old Roman Republic is the army rather than the state recruited the soldiers. Starting with Julius Caesar and the early Roman Emperors the Roman armies more loyal to their generals than to Rome, which meant that the empire would often be embroiled in civil wars when competing generals fought to be Emperor. The system was reformed after the Roman Empire nearly tore itself apart during the reign of Emperor Diocletian, who established a bureaucracy to administer both the military and empire, dividing the empire into a more easily administered Western and Eastern divisions.
Roman armies similar to modern armies, new soldiers had to go through a four-month boot camp located near the Tiber River. Taught how to use a sword, spear, bow and arrow, darts and slings, and how to swim, build a camp, and practice formations. They fought in formation somewhat like the hoplites, but more mobile, but more like the army of Alexander. The Roman army was organized into legions, they would charge when they were about thirty yards from their enemy, hurling their spears
Like the Greeks, they had a shield, helmet and breastplate, spear, dagger and sword, all weighing over sixty pounds. In addition, they marched with the tools needed to build a camp, pickaxe, saw, space, and basket for moving earth. When they weren’t fighting they built and maintained the road system of the Roman empire and other infrastructure like bridges
 Robert Garland, The Other Side of History, Lecture 25, Being a Roman Soldier