Over the course of the Spring and Autumn period, regional feudal lords consolidated and absorbed smaller powers; by 476 BCE, seven prominent states were left, all led by individual kings. The second part of the Eastern Zhou period is known as the Warring States period; during this time these few remaining states battled each other for total power.
Conflict Among the Seven States
The king by now was powerless, and the rulers of the seven independent states began to refer to themselves as kings as well. These major Chinese states were in constant competition. Since none of the states wanted any one rival to become too powerful, if one state became too strong, the others would join forces against it, so no state achieved dominance. This led to nearly 250 years of inconclusive warfare that became larger and larger in scale. It was also at this point that there first emerged the concept of a Chinese emperor who would rule over all the various kings, though the first Chinese emperors did not rule until China was unified under the later Qin Dynasty. The crossbow was invented, and its low cost and easy use (as compared to the expensive chariot) resulted in the increased conscription of peasants as expandable infantry.
Technological and Philosophical Development
The Iron Age had reached China by 600 CE, but it was during this period that the age spread and took root in China: by the time of the Warring States Period, China saw a widespread adoption of iron tools and weapons that were significantly stronger than their bronze counterparts.
This period also saw the further development of the philosophical movements that originated in the Hundred Schools of Thought of the Spring and Autumn period. Mencius further developed Confucian philosophy, expanding upon its doctrines and asserting the innate goodness of the individual and the importance of destiny. Daoism, Legalism, and Mohism became more developed. Archaic writing also gave way to a far more recognizable form of Chinese script.
Cultural, Economic, and Social Development
Two fundamental Chinese social characteristics had become apparent by this time: l) the concept of the patrilineal family as the basic unit in society, with high importance placed on blood relations, and 2) the concept of natural social differentiation into classes, each regarded in terms of their contributions to society.
Large-scale projects, like the Dujiangyan Irrigation System and the Zhengguo Canal, were carried out. Sophisticated arithmetic was carried out, including two digit decimal multiplication.
The Zuo Commentary on the Spring and Autumn Annals was a literary achievement. In other literary works, sayings of philosophers of the period were recorded in the Analects and the Art of War.
The Rise of the Qin State and Resolution of the Warring States Period
Though the military rivalries and alliances in the Warring States period were complex and constantly in flux, over time the Qin state, under the leadership of King Zheng, emerged as the most powerful. The Qin were particularly strongly rooted in Legalist philosophy, which advocated the importance of the state at the expense of the individual. They were also known for being ruthless and ignoring etiquette and protocol of war in order to win at all costs. In particular, Shang Yang, adviser to Zheng, enacted laws to force subjects of the kingdom to act in ways that helped the state; he forced them to marry early, have many children, and produce certain quotas of food. Ultimately, in 221 BCE, the Qin state conquered the others and established the Qin Dynasty.