The state of Qin was originally located in the western border region, starting as a tribe surnamed Ying living near Qinting (present-day Zhangjiachuan, Gansu). In the early Zhou Dynasty, it developed into a small state. When King Ping moved the capital eastward, Duke Xiang of Qin provided crucial assistance, for which he was enfeoffed as a feudal lord and granted the land west of Mount Qi, establishing the capital at Yong (south of present-day Fengxiang, Shaanxi). At the beginning of Duke Xiang's formal establishment of the state, Qin was small and weak, and during the Spring and Autumn period when major states vied for hegemony, it could not compare with the powerful states. Later, through the reigns of Dukes Wen, Xian, Wu, De, and Xuan, Qin's territory continuously expanded eastward. By the time Duke Mu ascended the throne, the state's power gradually grew strong, occupying most of the Guanzhong region.
Duke Mu of Qin, named Renhao, reigned for 39 years (659–621 BCE) and was a highly accomplished ruler in Qin's history. During his reign, he diligently governed and cared for the people domestically while actively expanding externally, incorporating present-day Gansu and Ningxia into his territory, thus initiating Qin's quest for hegemony among the feudal lords. He is recognized in some historical records as one of the Five Hegemons of the Spring and Autumn period.
In 659 BCE, Duke Mu of Qin ascended the throne, and that very year he personally led his army across the Yellow River to eliminate the Rong people at Maojin (east of present-day Ruicheng, Shanxi), beginning his campaign to expand his territory. Ambitious and determined to dominate the realm, Duke Mu of Qin was frustrated by the lack of wise and capable ministers to assist him, so he searched far and wide for talent. In his later years, he asked the renowned horse expert Bole to recommend someone skilled in judging horses. Bole then recommended his friend Jiufang Gao. Duke Mu summoned Jiufang Gao and sent him to find a fine horse. Three months later, Jiufang Gao reported that he had found a magnificent horse by a sand dune—a yellow mare. When Duke Mu sent someone to retrieve the horse, however, it turned out to be a black stallion. Disappointed, Duke Mu said to Bole, "Your friend cannot even tell a horse's color or gender—how can he judge what makes a good horse?" Bole replied, "A truly fine horse is not judged by its outward form, appearance, or bones, but by its elusive, almost intangible spirit. Jiufang Gao perceives the inner essence and core of a horse while overlooking its superficial traits; he values what truly matters and disregards what is unimportant. His method of judging horses holds value far beyond mere horse selection." Duke Mu was skeptical but later tested the horse and found it to be an exceptionally rare and outstanding steed. This experience greatly inspired him, so he sent people everywhere to seek out talent and began selecting officials without rigid standards, thereby attracting wise and virtuous individuals from across the land.
Duke Mu of Qin was determined to expand eastward, and the first obstacle in his path was his eastern neighbor, the State of Jin. Feeling threatened, Duke Xian of Jin actively conquered smaller surrounding states to expand his territory and strengthen his power. Later, Duke Xian of Jin used the strategy of borrowing a path to destroy the states of Yu and Guo, thereby taking control of the Xiaohan region, which blocked the crucial passage from the Guanzhong area to the Central Plains and hindered Qin's eastward advance.
In the fifth year of Duke Mu of Qin's reign, seeking to dominate the other states, he proposed a marriage alliance with the state of Jin. Duke Xian of Jin agreed and married his daughter Mu Ji to Duke Mu of Qin. When Duke Xian of Jin destroyed the state of Yu, he captured its ruler along with his minister Bai Li Xi, and subsequently sent Bai Li Xi as a slave accompanying the bride to Qin. On the road to Qin, Bai Li Xi secretly escaped and fled to Wan (present-day Nanyang, Henan), where he was captured by the people of Chu. When Duke Mu of Qin learned that Bai Li Xi was a talented and virtuous man, he urgently sent people to find him. By then, Bai Li Xi had already been taken by Chu, so Duke Mu of Qin ransomed him with five sheepskins and appointed him as a high-ranking minister. Bai Li Xi declined, saying that his friend Jian Shu was far more insightful and capable, a true sage of the time, and urged Duke Mu of Qin to employ Jian Shu instead, while he himself would willingly serve as Jian Shu's assistant.
Duke Mu of Qin sent someone to bring Jian Shu to the Qin state and sought his advice on how to establish a strong state. Jian Shu said that to establish a state, one must use both virtue and authority, but virtue and righteousness are the foundation, while punishment and power can only serve as supplements. If one solely emphasizes benevolence and virtue without using punishment to establish authority, the state cannot become strong; if one relies only on punishment and power without spreading benevolence and virtue, the people's hearts will be lost. Duke Mu of Qin then asked how to become a hegemon among the feudal lords. Jian Shu pointed out that to dominate the feudal lords, one must build trust with all states, avoid greed for small gains and rash, impatient ideas, and also assess the situation clearly, prioritizing urgent matters over less pressing ones. Duke Mu further asked how Qin could dominate the Central Plains. Jian Shu said that Duke Huan of Qi's hegemony was already in decline. Qin was located in the west and should first pacify the Rong and Di tribes to secure its rear, while waiting for changes in the Central Plains and building up its military strength. Then, it would be only a matter of time before Qin could replace Qi's position as the dominant power. Jian Shu's great talent and strategy deeply impressed Duke Mu of Qin, who then appointed Jian Shu and Bai Li Xi as the left and right prime ministers to jointly govern the state.
In the ninth year of Duke Mu's reign (651 BCE), Duke Xian of Jin died, and Jin fell into internal turmoil over succession struggles. Duke Mu of Qin sent Baili Xi with troops to welcome the exiled Prince Yiwu back to Jin to take the throne, who became Duke Hui of Jin. Previously, Duke Hui of Jin had promised to cede eight cities west of the Yellow River to Qin as thanks for helping him ascend the throne, but after taking power, he reneged on his word. Pi Bao, a minister of Jin, fled to Qin and was given an important position by Duke Mu.
In 648 BCE, the State of Jin suffered a severe drought, and Duke Mu of Qin generously sent them large quantities of grain to help them through the crisis. Two years later, when Qin faced a famine, Jin not only failed to repay this kindness by aiding Qin but instead took advantage of the situation, launching a military attack on Qin the following year. The two states clashed fiercely at Hanyuan, where Qin forces captured Duke Hui of Jin alive. Subsequently, through the mediation of King Xiang of Zhou and Mu Ji, Qin and Jin formed an alliance. Duke Hui of Jin sent his crown prince Yu to Qin as a hostage and ceded the land west of the Yellow River to Qin, after which Duke Mu of Qin released him. This battle expanded Qin's eastern border all the way to Longmen.
Duke Mu of Qin originally intended to continue expanding eastward into the Central Plains region. In 625 BCE, ignoring the remonstrations of Jian Shu, he dispatched troops to Mount Xiao, only to have three generals captured and his entire army annihilated. With Jin blocking the throat of Qin's eastward advance, Duke Mu decided to turn westward for development.
At that time, to the west of the Qin state lived dozens of large and small Rong and Di tribes and minor states, such as the Kun Rong, Mian Zhu, and Di west of Long Mountain, the Yiqu, Wushi, and Quyan Rong north of the Jing River, the Dali Rong in the Luo River region, and the Lu Hun Rong south of the Wei River, each with its own chieftain and independent rule. Among these tribes, the more powerful were the Mian Zhu (in present-day eastern Tianshui, Gansu), the Yiqu (in present-day northern Ningxia, Gansu), and the Dali (in present-day eastern Dali, Shaanxi). However, their production methods were backward, and they retained many primitive living habits. The Di and Rong were strong and fierce, skilled in horseback riding and archery, with a wild nature, often launching surprise attacks on Qin's border regions, burning, killing, and plundering, disrupting the peace and stability of the Qin people.
Under the guidance of virtuous ministers like Jian Shu and Bai Li Xi, the State of Qin developed rapidly, which also drew the attention of the Di and Rong tribes. Therefore, when Duke Mu of Qin expanded westward, he acted with great caution, adopting a strategy of first striking the strong, then the weak, and defeating them one by one. Among these tribes, the Mianzhu tribe of the Western Rong lived in an area bordering Qin territory. Hearing of Duke Mu's wisdom, the King of Mianzhu sent his advisor, You Yu, to observe the situation.
To intimidate the various Di and Rong tribes, Duke Mu of Qin gave a grand reception to You Yu, flaunting his national power by showing off the splendid palaces and abundant grain reserves of Qin, while also learning from him about the terrain and military strength of the Western Rong. Wanting to win You Yu over, the court official Liao suggested that since the Western Rong were isolated and likely lacked music and dance, sending female entertainers to the King of Mianzhu would surely sap his will. So Duke Mu selected twelve beautiful female musicians and sent them to the King of Mianzhu. The enchanting music and graceful dances so delighted the king that he indulged in drinking and pleasure, neglecting state affairs. Soon, the governance of Mianzhu fell into chaos. Only then did Baili Xi allow You Yu to return home. After returning, You Yu urged the Rong king to attend to state matters, but the king ignored him, worsening their relationship. Taking advantage of this, Duke Mu of Qin sent someone to persuade You Yu, treating him with courtesy, and eventually won his allegiance to Qin.
Having lived among the Rong people for a long time, Youyu was very familiar with their living conditions, customs, and terrain, so Duke Mu of Qin discussed with him strategies for unifying the western Rong tribes. With Youyu's help, in 623 BC, Baili Xi led troops to surround Mianzhu, and the king of Mianzhu, still enjoying his wine, was captured alive by the Qin army. Then, following Youyu's plan, the state of Qin successively destroyed dozens of kingdoms established by the Rong people in the west, expanding its territory by over a thousand li.
The Qin state conquered the Di and Rong tribes, eliminating threats from the west. Upon hearing the news, King Xiang of Zhou was overjoyed and specially sent the Duke of Shao to present golden drums as a gesture of congratulations, hoping that he would continue to beat the drums and pacify the Rong people's attacks—an event historically known as "Duke Mu of Qin Dominates the Western Rong."
The westward expansion greatly enlarged the territory of the Qin state, even bringing the Ba state in the southwest to pay homage. At this time, Qin's borders stretched from the Yellow River in the east, to Didao (present-day Lintao, Gansu) in the west, south to the Qinling Mountains, and north to the Quyan Rong (present-day Yanchi, Ningxia).