Seven Chinese states fought until Qin’s 221 BC unification
China’s Warring States era (c. 475–221 BC) closed the Zhou dynasty with relentless war, bureaucratic reform, and consolidation. Sima Qian’s start date of 475 BC is the usual textbook pick as Eastern Zhou kings shrank to ceremonial shadows.
Seven great powers defined the board: Qin west, Qi east, Chu south, Yan north, and the Three Jins—Wei, Han, Zhao—in the centre after Jin’s civil war among Han, Wei, Zhao, and Zhi clans ended around 453 BC. Hundreds of smaller polities had already coalesced as Zhou authority withered after the 771 BC flight east to the Luoyang region.
By 450 BC eight large states including Yan and Yue still dotted the map, yet the next 225 years of nearly continuous fighting belonged to the reformed armies and legalist administrations of the big seven. Military and civil innovations outpaced the Son of Heaven’s tiny enclave.
Jin's breakup was formalised in stages. In 403 BC King Weilie of Zhou raised the viscounts of Zhao, Wei and Han to marquises, and in 376 BC the three deposed Duke Jing of Jin and split his last territory. In Qi the Tian family usurped power, and the Zhou court recognised them partly to avoid being overwhelmed by stronger states. Wei under Marquess Wen became for a time the mightiest state, with Bu Shang, a former student of Confucius, tutoring at court; under King Hui it survived a Qi attack in 340 BC only because Chu came to its aid.
Qin's rise began with Shang Yang, whom Duke Xiao made prime minister over objections that his plans were radical, and who stayed in power for 20 years. He overhauled taxes, standardised weights and measures, promoted the nuclear family, carved the state into counties run by appointed magistrates and imposed a notoriously harsh legal code. Qin then took fertile land along the upper Yangzi, and in 325 BC its ruler Huiwen proclaimed himself king. Rivals answered with Su Qin's Vertical Alliances while Qin herded neighbours into Zhang Yi's Horizontal Alliances, and a coalition assault in 318 BC fell apart after a failed attack at the Hangu Pass. Qin finished its conquests in 221 BC, founding imperial China.
Source: Warring States period
