The Spring and Autumn period (c. 770 – c. 481 BCE) was a period in Chinese history corresponding roughly to the first half of the Eastern Zhou (c. 771 – 256 BCE), characterized by the gradual erosion of royal power as local lords nominally subject to the Zhou exercised increasing political autonomy. The period's name derives from the Spring and Autumn Annals, a chronicle of the state of Lu between 722 and 481 BCE, which tradition associates with Confucius (551–479 BCE).
During this period, local polities negotiated their own alliances, waged wars against one another, up to defying the king's court in Luoyi. The gradual Partition of Jin, one of the most powerful states, is generally considered to mark the end of the Spring and Autumn period and the beginning of the Warring States period. The periodization dates to the late Western Han (c. 48 BCE – 9 CE).
In 771 BCE, a Quanrong invasion in coalition with the states of Zeng and Shen—the latter polity being the fief of the grandfather of the disinherited crown prince Yijiu—destroyed the Western Zhou capital at Haojing, killing King You and establishing Yijiu as king at the eastern capital Luoyi. The event ushered in the Eastern Zhou dynasty, which is divided into the Spring and Autumn and the Warring States periods. During the Spring and Autumn period, China's fengjian system became largely irrelevant. The Zhou court, having lost its homeland in the Guanzhong region, held nominal power, but had real control over only a small royal demesne centered on Luoyi. During the early part of the Zhou dynasty period, royal relatives and generals had been given control over fiefdoms in an effort to maintain Zhou authority over vast territory. As the power of the Zhou kings waned, these fiefdoms became increasingly independent states.
The most important states (known later as the twelve vassals) came together in regular conferences where they decided important matters, such as military expeditions against foreign groups or against offending nobles. During these conferences one vassal ruler was sometimes declared hegemon.
As the era continued, larger and more powerful states annexed or claimed suzerainty over smaller ones. By the 6th century BCE, most small states had disappeared and just a few large and powerful principalities dominated China. Some southern states, such as Chu and Wu, claimed independence from the Zhou, who undertook wars against some of them (Wu and Yue).
Amid the interstate power struggles, internal conflict was also rife: six elite landholding families waged war on each other inside Jin, political enemies set about eliminating the Chen family in Qi, and the legitimacy of the rulers was often challenged in civil wars by various royal family members in Qin and Chu. Once all these powerful rulers had firmly established themselves within their respective dominions, the bloodshed focused more fully on interstate conflict in the Warring States period, which began in 403 BCE when the three remaining elite families in Jin—Zhao, Wei and Han—partitioned the state.
Early Spring and Autumn (771–685 BCE)
After the Zhou capital was sacked by the Marquess of Shen and the Quanrong barbarians, the Zhou moved the capital east from the now desolated Zongzhou in Haojing near modern Xi'an to Wangcheng in the Yellow River Valley. The Zhou royalty was then closer to its main supporters, particularly Jin, and Zheng; the Zhou royal family had much weaker authority and relied on lords from these vassal states for protection, especially during their flight to the eastern capital. In Chengzhou, Prince Yijiu was crowned by his supporters as King Ping. However, with the Zhou domain greatly reduced to Chengzhou and nearby areas, the court could no longer support the six army groups it had in the past; Zhou kings had to request help from powerful vassal states for protection from raids and for resolution of internal power struggles. The Zhou court would never regain its original authority; instead, it was relegated to being merely a figurehead of the regional states and ritual leader of the Ji clan ancestral temple. Though the king retained the Mandate of Heaven, the title held little actual power.
With the decline of Zhou power, the Yellow River drainage basin was divided into hundreds of small, autonomous states, most of them consisting of a single city, though a handful of multi-city states, particularly those on the periphery, had power and opportunity to expand outward. A total of 148 states are mentioned in the chronicles for this period, 128 of which were absorbed by the four largest states by the end of the period.
Shortly after the royal court's move to Chengzhou, a hierarchical alliance system arose where the Zhou king would give the title of hegemon (霸) to the leader of the state with the most powerful military; the hegemon was obligated to protect both the weaker Zhou states and the Zhou royalty from the intruding non-Zhou peoples: the Northern Di, the Southern Man, the Eastern Yi and the Western Rong. This political framework retained the fēngjiàn power structure, though interstate and intrastate conflict often led to declining regard for clan customs, respect for the Ji family, and solidarity with other Zhou peoples. The king's prestige legitimized the military leaders of the states, and helped mobilize collective defense of Zhou territory against "barbarians".
Over the next two centuries, the four most powerful states—Qin, Jin, Qi and Chu—struggled for power. These multi-city states often used the pretext of aid and protection to intervene and gain suzerainty over the smaller states. During this rapid expansion, interstate relations alternated between low-level warfare and complex diplomacy.
Zheng falls out with the court (722–685)
Duke Yin of Lu ascended the throne in 722. From this year on, the state of Lu kept an official chronicle, the Spring and Autumn Annals, which along with its commentaries is the standard source for the Spring and Autumn period. Corresponding chronicles are known to have existed in other states as well, but all but the Lu chronicle have been lost.
In 717, Duke Zhuang of Zheng went to the capital for an audience with King Huan. During the encounter the duke felt he was not treated with the respect and etiquette which would have been appropriate, given that Zheng was now the chief protector of the capital. In 715, Zheng also became involved in a border dispute with Lu regarding the Fields of Xu. The fields had been put in the care of Lu by the king for the exclusive purpose of producing royal sacrifices for the sacred Mount Tai. For Zheng to regard the fields as just any other piece of land was an insult to the court.
By 707, relations had soured enough that the king launched a punitive expedition against Zheng. The duke counterattacked and raided Zhou territory, defeating the royal forces in the Battle of Xuge and injuring the king himself. Zheng was the first vassal to openly defy the king, kicking off the centuries of warfare without respect for the old traditions which would characterize the period.
The display of Zheng's martial strength was effective until succession problems after Zhuang's death in 701 weakened the state.
In 692, there was a failed assassination attempt against King Zhuang, orchestrated by elements at court.
The Five Hegemons (685–591 BCE)