Ancient warfare
The overthrow of the Shang by the Zhou saw the creation of a feudal social order, resting militarily on a class of aristocratic chariot warriors (士).
In the Spring and Autumn period, warfare increased. Zuo zhuan describes the wars and battles among the feudal lords during the period. Warfare continued to be stylised and ceremonial even as it grew more violent and decisive. The concept of military hegemon (霸) and his "way of force" (霸道) came to dominate Chinese society. Sun Tzu created a book that still applies to today's modern armies, The Art of War.
Formations of the army can be clearly seen from the Terracotta Army of Qin Shi Huang, the first Emperor in the history of China to be successful in the unification of different warring states. Light infantry acting as shock troops lead the army, followed by heavy infantry as the main body of the army. Wide usage of cavalry and chariots behind the heavy infantry also gave the Qin army an edge in battles against the other warring states.
Warfare became more intense, ruthless and much more decisive during the Warring States period, in which great social and political change was accompanied by the end of the system of chariot warfare and the adoption of mass infantry armies. Cavalry was also introduced from the northern frontier, despite the cultural challenge it posed for robe-wearing Chinese men. Chinese river valley civilizations would adopt nomadic "pants" for their cavalry units and soldiers.

Japanese: Horses and bows were very important in Japan and were used in warfare from very early times, as shown in statues and artifacts found in tombs of early chieftains. Samurai eventually became very skilled in using the horse. Because their main weapon at this time was the bow and arrow, early samurai exploits were spoken of in Japanese war tales as the "Way of the Horse and Bow." Horse and bow combined was a battlefield advantage to the early samurai. A bunch of arrows made of mainly wood with poison-tipped points was worn on a warrior's right side so he could quickly knock and release an arrow mid-gallop.
Although they weren't as important as the bow, swords of various sizes and types were also part of an early samurai's armory. They were mostly for close-quarters engagements. Many different kinds of spears were also used. One, the naginata, was a curved blade fixed to the end of a pole several feet long. This was known as a 'woman's spear' because samurai girls were taught to use it from an early age. A device called the kumade, which resembled a long-handled garden rake, was used to catch the clothing or helmet of enemy horsemen and unseat them.
Common samurai archers had armor made of lamellae pieces laced together with colorful cords. The lightweight armor allowed for greater freedom of movement, faster speed, and reduced fatigue for horse and rider.
The early Yamato period had seen a continual engagement in the Korean Peninsula until Japan finally withdrew, along with the remaining forces of the Baekje Kingdom. Several battles occurred in these periods as the Emperor's succession gained importance. By the Nara period, Honshū was completely under the control of the Yamato clan. Near the end of the Heian period, samurai became a powerful political force, thus starting the feudal period.

Ancient Greece: In general, most features of the hoplite panoply of classical Greek antiquity, were already known during the Late Bronze Age by Mycenaean Greeks (c. 1600–1100 BC). Mycenaean Greek society invested in the development of military infrastructure, while military production and logistics were supervised directly from the palatial centers.
Infantry did almost all of the fighting in Greek battles. The Greeks did not have any notable cavalry tradition except the Thessalians. Hoplites, Greek infantry, fought with a long spear and a large shield, the aspis. Light infantry (psiloi) peltasts, served as skirmishers.
Despite the fact that most Greek cities were well fortified (with the notable exception of Sparta) and Greek siege technology was not up to the task of breaching these fortifications by force, most land battles were pitched ones fought on flat-open ground. This was because of the limited period of service Greek soldiers could offer before they needed to return to their farms; hence, a decisive battle was needed to settle matters at hand. To draw out a city's defenders, its fields would be threatened with destruction, threatening the defenders with starvation in the winter if they did not surrender or accept battle.

This pattern of warfare was broken during the Peloponnesian War, when Athens' command of the sea allowed the city to ignore the destruction of the Athenian crops by Sparta and her allies by shipping grain into the city from the Crimea. This led to a warfare style in which both sides were forced to engage in repeated raids over several years without reaching a settlement. It also made sea battle a vital part of warfare. Greek naval battles were fought between triremes – long and speedy rowing ships which engaged the enemy by ramming and boarding actions.

Hellenistic Era: During the time of Philip II of Macedon and Alexander the Great, the Macedonians were regarded as the most complete well co-ordinated military force in the known world. Although they are best known for the achievements of Alexander the Great, his father Philip II of Macedon created and designed the fighting force Alexander used in his conquests. Before this time and for centuries their military prowess was nowhere near that the sarissa phalanx offered.
However, prior to the improvements made by Philip II of Macedon armies fought in the traditional manner of the Greeks; that of the hoplite phalanx.
Philip provided his Macedonian soldiers in the phalanx with sarissa, a spear which was 4–6 meters in length. The sarissa, when held upright by the rear ranks of the phalanx (there were usually eight ranks), helped hide maneuvers behind the phalanx from the view of the enemy. When held horizontal by the front ranks of the phalanx, enemies could be run through from far away. The hoplite type troops were not abandoned, but were no longer the core of the army.
In 358 BC he met the Illyrians in battle with his reorganized Macedonian phalanx and utterly defeated them. The Illyrians fled in panic, leaving the majority of their 9,000-strong army dead. The Macedonian army invaded Illyria and conquered the southern Illyrian tribes.
After the defeat of the Illyrians, Macedon's policy became increasingly aggressive. Paeonia was already forcefully integrated into Macedon under Philip's rule. In 357 BC Philip broke the treaty with Athens and attacked Amphipolis which promised to surrender to the Athenians in exchange for the fortified town of Pydna, a promise he didn't keep. The city fell back in the hands of Macedonia after an intense siege. Then he secured possession over the gold mines of nearby Mount Pangaeus, which would enable him to finance his future wars.
In 356 the Macedonian army advanced further eastward and captured the town of Crenides (near modern Drama) which was in the hands of the Thracians, and which Philip renamed after himself to Philippi. The Macedonian eastern border with Thrace was now secured at the river Nestus (Mesta).

Philip next marched against his southern enemies. In Thessaly he defeated his enemies and by 352, he was firmly in control of this region. The Macedonian army advanced as far as the pass of Thermopylae which divides Greece in two parts, but it did not attempt to take it because it was strongly guarded by a joint force of Athenians, Spartans, and Achaeans.
Having secured the bordering regions of Macedon, Philip assembled a large Macedonian army and marched deep into Thrace for a long conquering campaign. By 339 after defeating the Thracians in series of battles, most of Thrace was firmly in Macedonian hands save the most eastern Greek coastal cities of Byzantium and Perinthus who successfully withstood the long and difficult sieges. But both Byzantium and Perinthus would have surely fallen had it not been for the help they received from the various Greek city-states, and the Persian king himself, who now viewed the rise of Macedonia and its eastern expansion with concern. Ironically, the Greeks invited and sided with the Persians against the Macedonians, although Persia had been the nation hated the most by Greece for more than a century. The memory of the Persian invasion of Greece some 150 years ago was still alive, but the current politics for the Macedonians had put it aside.
Much greater would be the conquests of his son, Alexander the Great, who would add to the phalanx a powerful cavalry, led by his elite Companions, and flexible, innovative formations and tactics. He advanced Greek style of combat, and was able to muster large bodies of men for long periods of time for his campaigns against Persia.

Iron Age Europe: 

Roman Empire: The Roman army was the world's first professional army. It had its origins in the citizen army of the Republic, which was staffed by citizens serving mandatory duty for Rome. The reforms of Marius around 100 BC turned the army into a professional structure, still largely filled by citizens, but citizens who served continuously for 20 years before being discharged.