[5] According to the 2nd-century BC Records of the Grand Historian by Sima Qian, the Qin state traced its origin to Zhuanxu, one of the legendary Five Emperors in ancient times.

[6][7] The western Ying clan at Quanqiu were lords over the Xichui ('western march') region west of Mount Long and served as a buffer state for the Shang dynasty against invasions by the Xirong barbarians.

[6][8] Scholars such as Annette Juliano and Arthur Cotterel have suggested that having a horse-breeder as their ancestor may imply that the Ying family had a partial connection to nomadic tribes.

The Xirong tribes seized this opportunity to rebel against the Zhou dynasty, attacking and exterminating the senior branch of the Ying clan at Quanqiu.

After King Xuan of Zhou ascended the throne in 827 BC, he appointed Qin Zhong, Feizi's great-grandson, as the commander of his forces in the campaign against the Xirong.

When Duke Zhuang died in 778 BC, his eldest son Shifu chose to continue fighting the Xirong and avenge their grandfather, turning down the succession.

In 777 BC, Duke Xiang married his younger sister, Mu Ying, to a Rong leader named King Feng (豐王) in an apparent attempt to make peace.

Encouraged by this promise, the following generations of Qin rulers launched several military campaigns against the Rong, eventually expanding their territories far beyond the original lands lost by the Western Zhou dynasty.

The Qin forces were defeated at the Battle of Xiao (near modern Luoning County, Henan) and suffered heavy casualties, and all three of its generals were captured.

Duke Mu refused to advance further east after holding a memorial service for those killed in action at the Battle of Xiao and returned to focus on the traditional policy of expanding Qin's dominance in the west.

Duke Mu's achievements in Qin's western campaigns and his handling of foreign relations with Jin earned him a position among the Five Hegemons of the Spring and Autumn period.

The famous poem, "No Clothes" (Chinese: 無衣; pinyin: Wú Yī), recorded in the Classic of Poetry, was a battle hymn personally composed by Duke Ai to boost the morale of the Qin troops.

Initially, Qin avoided involvement using its protective geography and, responding to growing external threats, gradually turned to intervention in the manner of "defensive imperialism.

He issued an announcement inviting men of talent (including scholars, administrators, theorists, and militarists) from other states to enter Qin and assist him with his reforms, promising rewards of high offices and lands in return.

"[29] By the late 4th century BC, other states in China became alarmed by the Qin power and began forming anti-hegemonic alliances, called Perpendicular (Sima Qian 5:208; 6:279).

The Qin kings authorised numerous state development projects, including significant public works such as irrigation canals and defensive structures.

Following Shang Yang's reforms, the aristocracy system was abolished and replaced by a meritocracy, in which ordinary citizens had the same opportunities as the nobles to be promoted to high ranks.

Simultaneously, Qin's strategic position in Ba and Shu provided it with a platform for launching attacks on the Chu state, which lies downstream of the Yangtze.

Although Chu had the largest operation-ready army of all the Seven Warring States at over a million troops,[citation needed] its administrative and military strength was plagued by corruption and divided among the nobles.

In the early years of King Zhaoxiang's reign, the Marquis of Rang (穰侯) served as Qin's chancellor and actively advocated for military campaigns against the state of Qi in the far eastern part of China.

King Zhaoxiang heeded this advice and altered Qin's foreign policy to foster good diplomatic relations with the distant states of Yan and Qi), while focusing on attacking the nearby Zhao, Han, and Wei.

As a result, Qin began to launch constant attacks on Han and Wei over the subsequent decades, conquering several territories in its campaigns.

Although Qin had an abundance of resources and vast manpower, it had to enlist every man above the age of 15 for war-related duties, ranging from front-line service to logistics and agriculture.

Within Zhao, many officials strongly opposed King Xiaocheng's decision to give up the cities, and subsequent delays caused the siege on Handan to be prolonged until 258 BC.

In 257 BC, Qin was still unable to penetrate Handan after besieging it for three years, and Zhao requested aid from the neighbouring states of Wei and Chu.

In the middle of the 3rd century, Zheng Guo, a hydraulic engineer from the state of Han, was dispatched to Qin to advise King Zhaoxiang on the construction of irrigation canals.

Qin benefited from the project as it became one of the most fertile states in China due to the efficient irrigation system, and also because it could now muster more troops as a result of increased agricultural yield.

Its people were unspoiled and exceedingly deferential; its officers unfailingly respectful, earnest, reverential, loyal, and trustworthy; and its high officials public-spirited, intelligent, and assiduous in the execution of the duties of their position.

"[35] In his Petition against driving away foreigners (諫逐客書), Li Si mentioned that the guzheng and percussion instruments made of pottery and tiles were characteristic of Qin music.

[37] Qin is also represented by the star Delta Serpentis in the Right Wall asterism, part of the Heavenly Market enclosure (see Chinese constellation).