The Warring States Period saw the proliferation of in China, replacing bronze as the dominant metal used in warfare. Areas such as and were also brought into the Chinese cultural sphere during this time. Different philosophies developed into the Hundred Schools of Thought, including Confucianism , Taoism , and Mohism . Trade also became important, and some merchants had considerable power in politics. Military tactics also changed. Unlike the Spring and Autumn Period, most armies in the Warring States Period made combined use of infantry and cavalry, and the use of chariots gradually fell into disfavor. Thus from this period on, the nobles in China remained a literate rather than warrior class, as the kingdoms competed by throwing masses of soldiers against each other. Arms of soldiers gradually changed from bronze to unified iron arms. Dagger-axes were an extremely popular weapon in various kingdoms, especially for the Qin who produced eighteen-foot long pikes.
This was also around the time the legendary military strategist Sun Tzu wrote ''The Art of War'' which is recognized today as the most influential, and oldest known military strategy guide. Along with this are other military writings that make up the Seven Military Classics of ancient China: 's Six Secret Teachings, The Methods of the Sima, Sun Bin's Art of War, Wu Qi, Wei Liaozi, Three strategies of Huang Shigong, and The Questions and Replies of Tang Taizong and Li Weigong . Once China was unified, these seven military classics were locked away and access was restricted due to their tendency to promote revolution.
Partition of Jin
In the Spring and Autumn Period, the State of Jin was arguably the most powerful state in China. However, near the end of the Spring and Autumn Period, the power of the ruling family weakened, and gradually came under the control of six ministers belonging to six different families . By the beginning of the Warring States Period, after numerous power struggles, there were four families left: the Zhi family, the Wei family, the Zhao family, and the Han family, with the Zhi family being the dominant power in . Zhi Yao , the last head of the Zhi family, attempted a coalition with the Wei family and the Han family to destroy the Zhao family. However, because of Zhi Yao's arrogance and disrespect towards the other families, the Wei family and Han family secretly allied with the Zhao family, and the three families launched a surprise attack at Jinyang, which was besieged by Zhi Yao at the time, and annihilated the Zhi.
In 403 BC, the three major families of , with the approval of the Zhou king, partitioned Jin into three states, which was historically known as 'The Partition of Jin of the Three Families' . The new states were: the State of Han, the State of Zhao, and the State of Wei. The three family heads were given the title of Marquis , and because the three states were originally part of , they are also referred to as the Three Jins . The State of Jin continued to exist with a tiny piece of territory until 376 BC when the rest of the territory was partitioned by the Three Jins.
Change of government in Qi
In 389 BC, the Tian family seized control of the State of Qi, and were given the title of Duke. The old Jiang family's State of Qi continued to exist with a small piece of territory until 379 BC, when it was finally absorbed into Tian family's State of Qi.
Early strife in the Three Jins, Qi, and Qin
In 371 BC, Marquess Wu of Wei died without specifying a successor, causing to fall into an internal war of succession. After three years of civil war, and , sensing an opportunity, invaded . On the verge of conquering , the leaders of and fell into disagreement on what to do with and both armies mysteriously retreated. As a result, King Hui of Wei was able to jump onto the throne of .
In 354 BC, King Hui of Wei initiated a large scale attack at , which some historians believe was to avenge the earlier near destruction of . By 353 BC, was losing the war badly, and one of their major cities — Handan , a city that would eventually become 's capital — was being besieged. As a result, the neighbouring State of Qi decided to help . The strategy used, suggested by the famous tactician Sun Bin , a descendant of Sun Tzu, who at the time was the army advisor, was to attack 's territory while the main army is busy sieging , forcing to retreat. The strategy was a success; the army hastily retreated, and encountered the midway, culminating into the Battle of Guiling where was decisively defeated. The event spawned the idiom "?魏救?/围魏救赵", meaning ''"Surrounding to save "'', which is still used in modern Chinese to refer to attacking an enemy's vulnerable spots in order to relieve pressure being applied by that enemy upon an ally.
In 341 BC, attacked , and interfered again. The two generals from the previous Battle of Guiling met again, and due to the brilliant strategy of Sun Bin, was again decisively defeated at the Battle of Maling .
The situation for took an even worse turn when , taking advantage of series of defeats by , attacked in 340 BC under the advice of famous Qin reformer Shang Yang . was devastatingly defeated and was forced to cede a large portion of its territory to achieve a truce. This left their capital Anyi vulnerable, so was also forced to move their capital to Daliang.
After these series of events, became severely weakened, and the and states became the two dominant states in China.
Shang Yang's reforms in Qin
Around 359 BC, Shang Yang , a minister of the State of Qin, initiated a series of reforms based on the political doctrine of Legalism that transformed from a backward state into one that surpasses the other six states. It is generally regarded that this is the point where started to become the most dominant state in China.
Ascension of the Kingdoms
In 334 BC, the rulers of and agreed to recognize each other as Kings , formalizing the independence of the states and the powerlessness of the Zhou throne since the beginning of the . The King of and the King of joined the ranks of the King of , whose predecessors had been Kings since the Spring and Autumn Period. From this point on, all the other states eventually declare their Kingship, signifying the beginning of the end of the Zhou Dynasty.
In 325 BC, the ruler of declared himself as King.
In 323 BC, the rulers of and declared themselves as King.
In 318 BC, the ruler of , a relatively minor state, declared himself as King.
The ruler of held out until around 299 BC, and was the last to declare himself as King.
Chu expansion and defeats
Early in the Warring States Period, was one of the strongest states in China. The state rose to a new level of power around 389 BC when the King of named the famous reformer Wu Qi to be his prime minister.
rose to its peak in 334 BC, when it gained vast amounts of territory. The series of events leading up to this began when prepared to attack . The King of sent an emissary who persuaded the King of to attack instead. initiated a large scale attack at , but was devastatingly defeated by 's counter-attack. Chu then proceeded to conquer the State of Yue. This campaign expanded the Chu's borders to the coasts of the Pacific Ocean.
The Domination of Qin and the resulting Grand Strategies
Towards the end of the Warring States Period, the State of Qin became disproportionately powerful compared to the other six states. As a result, the policies of the six states became overwhelmingly oriented towards dealing with the Qin threat, with two opposing schools of thought: Hezong , or alliance with each other to repel Qin expansionism; and Lianheng , or alliance with Qin to participate in its ascendancy. There were some initial successes in Hezong, though it eventually broke down. Qin repeatedly exploited the Lianheng strategy to defeat the states one by one. During this period, many philosophers and tacticians travelled around the states recommending the rulers to put their respective ideas into use. These "lobbyists" were famous for their tact and intellect, and were collectively known as Zonghengjia , taking its name from the two main schools of thought.
In 316 BC, conquered the Shu area.
Around 300 BC, Qi was almost totally annihilated by a coalition of five states led by Yue Yi of Yan . Although under General Tian Dan Qi managed to recover their lost territories, it would never be a great power again. Yan was also too exhausted afterwards to be of much importance in international affairs after this campaign.
In 293 BC the Battle of Yique against Wei and Han resulted in victory for Qin. This effectively removed Wei and Han threat to further Qin aspirations.
In 278 BC, Qin attacked Chu and managed to capture their capital city, Ying, forcing the Chu king to move eastwards to Shouchun. This campaign virtually destroyed Chu's military might, although they recovered sufficiently to mount serious resistance against Qin 50 years later.
In 260 BC, the Battle of Changping was fought between Qin and Zhao, resulting in a catastrophic defeat for the latter. Although both sides were utterly exhausted after the titanic clash, Zhao, unlike Qin, could not recover after the event.
In about 50 years Qin superiority was secure, thanks to its powerful military and, in part, constant feuding between the other states.
The Warring States Period saw the introduction of many new innovations to the art of warfare in China, such as the use of iron and cavalry.
The various states fielded massive armies of infantry, cavalry and chariots. Complex logistical systems maintained by efficient government bureaucracy, was needed to supply, train, and control such large forces. The size of the armies ranged from tens of thousands to several hundred thousand men.
Iron became more widespread and began to replace bronze. Most armour and weapons of this period were made from iron.
The first official native Chinese cavalry unit was formed in 307 BC by King Wuling of Zhao.
But the war chariot still retained its prestige and importance, despite the tactical superiority of cavalry.
Crossbow was the preferred long range weapon of this period due to many reasons. The crossbow could be mass-produced easily, and mass training of crossbowmen was possible. These qualities made it a powerful weapon against the enemy.
Infantrymen deployed a varieties of weapons, but the most popular was the dagger-axe. The dagger-axe came in various length from 9?18 ft, the weapon comprising a thrusting spear with a slashing blade appended to it.
Zhao's military reforms
In 307 BC, King Wuling of Zhao adopted superior non-Chinese horse-riding clothing to better facilitate cavalry fighting tactics .
Qin's conquest of China
In 230 BC, the State of Qin conquers the State of Han when it, being the weakest state of the total seven Warring States and also being one of the neighbours to the much more stronger Qin and was being continuously assaulted by Qin in earlier years during Warring states period. This went on until Emperor Qin Shi Huang sent the famed general Wang Jian to attack the state of Zhao. King An of Han , frightened by the possibility that the State of Qin was going to target them right after Zhao, immediately sent diplomats to the state of Qin to surrender the entire kingdom without a fight. Although Qin had conquered Han without a fight, it also saved a lot of people from the potential devastation if the State of Han was to resist its massive invasions.
In 225 BC, conquers . The Qin army led a direct invasion into the state of Wei by besieging its capital Kaifeng but soon the Qin army realized that the city walls were too tough to break into and so they devised a new strategy in which they utilized the power of a local river which was linked to the Yellow River. The river was then used to flood the city's walls, causing massive devastation to the city. Upon realizing the situation, King Jia of Wei hurriedly came out of the city and surrendered its city to the Qin army in order to avoid further bloodshed of his people.
In 223 BC, invades . The King of Qin, Ying Zheng, decided to first defeat the strongest state, Chu. However, the first invasion was doomed to utter disaster when northern style Qin troops were defeated by 500,000 Chu troops in the unfamiliar territory of Huaiyang, modern-day northern Jiangsu and Anhui provinces. The Qin general was Li Xing, who was inexperienced.
In 224 BC., the famed conqueror of the state of Zhao, Wang Jian, was recalled to lead a second invasion with 600,000 men. Chu's morale was greatly increased after their success in defeating the seemingly invincible army of Qin the year before. The Chu forces were content to sit back and defend and believed it was Qin's intention to besiege Chu. However, Wang Jian tricked the Chu army by appearing to be idle in his fortifications whilst secretly training his troops to fight in Chu territory. After a year, Chu decided to disband due to inaction. Wang Jian invaded at the best moment with full force to overrun Huaiyang and the remaining Chu forces. Chu lost the initiative and could only sustain local guerrilla-style resistance until it too was fully conquered in 223 BCE. During their peak sizes, both armies of Chu and Qin combined numbered over 1,000,000 troops, more than the massive battle of Changping between Qin and Zhao 35 years before but which the Qin was able to conquer the state of Chu at last.
In 222 BC, conquers and . After the conquest of Zhao the Qin army then turned its attention towards the state of Yan. Realizing the danger & gravity of this situation, Yan Prince Dan had sent an assassin Jing Ke to kill the Qin emperor but this failure only helped to fuel the rage & determination of Qin Shi Huang and he increased the number of troops to conquer the state of Yan.
In 221 BC, conquers . Qi previously did not contribute or helped other states when Qin was conquering the other states and as soon as Qin was aiming for its final target the Qi quickly made the same decision as the Han did some nine years earlier and surrendered all its cites to Qin, completing the unification of China, and ushering in the Qin Dynasty.