Wars were common in ancient Greece. However, the ancient Greek wars known much about today thanks to the writing of Homer and Herodotus and Thucydides and Arrian are the Trojan War (sometime in 1250 BC but it may be a made-up story), the Persian Wars (490-480 BC), the Peloponnesian War (441-404 BC) and the campaigns of Alexander the Great (331-323 BC).
The Greek lived in city-states with population no larger than 100,000 people in each. This fractious nature of its society made organized warfare inevitable. They fought in their famous battle formation – the hoplite phalanx. When exactly this tactic occurred remains uncertain but it had certainly been complete by 650 BC. The hoplite was heavily armored, spear-armed citizen soldier, mostly from middle class. The phalanx composed of hoplites fighting in lines, shoulder to shoulder. The hoplite would lock their shields together and the first few ranks would project their spears out of the first rank of shields, which made frontal assaults very difficult for their opponents. This military formation maximized the effectiveness of armors, large shields and spears while creating an impenetrable wall of men.
Ancient Greek wars had usually occurred at small-scale, fought between similar phalanx of different city-states. Wars were seasonal, relatively local and low in intensity since soldiers had other occupations and more importantly, no side could afford enduring conflicts and casualties. Moreover, the lack of siege craft made it impossible for one side to attack the other if the latter refused the battle and retreated to their city. Thus, conflicts were more than often settled after single battles.
The Persian Wars (490-480 BC) had definitely changed the scale and scope of ancient Greek wars. These were the first true engagement of Greek army with non-Greek one. And no single city-state could effectively fight against such large army. This led to submission of many Greek city-states but also and more significantly the alliance of many other in defense, notably Athens and Sparta. The Persian wars witnessed the superiority of Greek well-trained hoplites against an enormous non-Greek army and also marked the alliance of Greek state-cities at an usual level as well as a diversification of armed forces: the introduction of a navy.
The rise of Athens and Sparta as predominant powers during this conflict finally led to the Peloponnesian War (441-404 BC), fought between pro-Athens and pro-Sparta leagues of cities. This was when ancient Greek wars saw further development of the nature of warfare, strategy and tactics. The accumulated manpower and financial resources enlarged war scale and facilitated the diversification of warfare. A new increased emphasis was placed on navies, sieges, mercenaries and economic warfare. The Spartan finally came to establish their dominance in Greece.
However, all Greek city-states came out of this long war worn out and poor. King Phillip of Macedon, a tribal kingdom to the north of Greece had taken their city-states one after the other. One major factor in the success of this conquest lied in the military innovations that Phillip had made: the use of diverse forces including strong cavalry; the development of phalanx into lightly armoured infantry armed with 6-metre-long spears who would pin down enemy’s for more mobile cavaltry to outflank. Alexander the Great, his son and successor, continued his conquest. With his adaptive strategies and combined-arms armies, Alexander had managed in his short life to extend Macedonian power not only over the central Greek city-states, but also to the Persian empire, including Egypt and lands as far east as the fringes of India, starting a period when Greek cultural influence and power was at its zenith in Europe and Asia.