Ancient China the 'Warring States Period' (453-221 BC)

It is impossible to develop on the 'warring kingdoms' era  (or China's way of warfare) without mentionning Sun Tzu, the legendary author of the famous 'art of war' which inspired so many generals throughout History (especially the japanese army of the twentieth century and Mao Tse Tung, as he claimed it himself).

In his treaty, Sun Tzu (considered as a mythic character) teach the reader about how to lead an army, when to fight or not, how to fight according to the type of terrain, what must be the traits of a good general...but more importantly, he gives an insight of the Chinese way of warfare as it was in his times : 

A 'Chinese' (at that time China wasn't united in one country but was divided into many little kingdoms, like 18th century Germany) army fielded about 100 000 men, relying mostly on bowmen and crossbowmen (however used in China since the fifth century BC, the crossbow wasn't known in Europe before the Middle Ages) but also on heavy infantry to form the backbone (or center) of any army, while light cavalry and light infantry would occupy the flanks (or wings) but this pattern could be reversed, as the Chinese didn't think like in the Western world in terms of 'center' and 'wings'.         For them, there was an 'impact force' (composed of heavy infantry units supported by the missile units) and a 'mobile force' (the light cavalry, obviously) which could switch positions according to the situation. 

Chinese conception of warfare was one of constant changes in tactics, and that's why there were so many great generals at that time. An army was compared to the sea : smashing everything which would be on its path, it would avoid the big rocks. On the field the ideal was to find the perfect sape, to anticipate the ennemy's moves while hiding yours, and it's very likeky that generals used on the battlefield the geometrical shapes that could be found in the Tao.

The 'Warring States'

This amazing way of considering warfare, which triggers our imagination by thinking war as a real art (like painting or drawing) and which definitely brought warfare at its esthetic climax (even the Romans, with their legendary maniples didn't have such a flexibility of mind in battle and Hannibal, considered as one of the greatest, if not the greatest, tacticians of the ancient times, only really innovated once : he won most of his battles against the Romans by essentially envelopping them, only opting for a different pattern as compared to the 'traditionnal' one at Cannes) while Chinese generals kept changing their tactics. Even if not always applied to the battlefield that was at least the ideal. To finish with, anyone who would be interested in ancient Chinese warfare (or in warfare in general) should watch one of the best movies dealing with this period : John Woo's The Three kingdoms, and of course read Sun Tzu's Art of War.

Ancient Assyria, the first regular army

If at the beginning of its history (2100 BC) the Assyrian empire only possessed an army of mere peasants pikemen, it quickly gained global supremacy in warfare thanks to two great innovations in weaponry : the use of the horse (war chariots) and of the iron (swords) combinated with a newly born administration (each warrior received a wage, specific buildings were created to store weapons, horses and food...). It gave to the Assyrian army two great advantages over the other powers (9th century BC) : a professionnal army (well trained, it would fight far better than levied peasants)  and in terms of technology (iron was more effective than bronze). This army relied upon a strong infantry as a backbone, and on chariots to protect its flanks. Very deadly in plain, it found itself also fairly good in uneven terrains (even if its chariots were uneffiicient in these conditions). More over, the Assyrians were fine siege crafters (they knew how to build towers, battering rams, engines able to throw burning materials on the walls...)