Which country finally succeeded through political reform during the Spring and Autumn Period and the Warring States Period?

During the Spring and Autumn Period and the Warring States Period, Qin was the last country to achieve success through political reform.

In the 13th year (356 BC) and 19th year (350 BC) of Zhou Xianwang, Qin Xiaogong appointed Shang Yang to carry out the most thorough political reform. Shang Yang's political reform encouraged population proliferation, emphasized agriculture and restrained business, abolished the system of "being an expensive official", rewarded military service, compiled household registration and implemented the law of "tongzhi". At that time, the state of Qin was vast in territory and abundant in resources, with a large population. Therefore, Shang Yang suggested that Qin Xiaogong should adopt preferential policies for foreign immigrants to attract Sanjin people to reclaim wasteland in Qin.

In the first 350 years, in order to deepen the reform and get rid of the interference of the old aristocratic forces, Qin Daliangzao (Shang Yang) proposed to move the capital from Yongcheng (now Fengxiang, Baoji) to the newly-built Xianyang City, which was well supported.

Wei Yang completely abolished the old stone-clearing system, established a new autocratic centralized system, and promoted the county system to strengthen centralized power, attaching importance to agricultural products, resulting in a prosperous scene of "giving enough to others". The people of the whole country are ashamed of private wars, thinking that the country is proud of its military achievements, and its combat effectiveness is constantly increasing. Wei Jun has been defeated in repeated wars, and Qin, a rich country in Qiang Bing, became the most powerful country at the end of the Warring States Period, and stood out in the west. Historical records record: "Nineteen years of filial piety, the son of heaven is a servant." King Xian of Zhou named Qin Jun as Fang Bo, which officially acknowledged his hegemony.