Zhang Yi: The Warring States Diplomat and the Strategy of "Horizontal Alliance" in Zizhi Tongjian

Brief Introduction

Zhang Yi (?–309 BC), a native of the State of Wei during the Warring States period, is a famous representative of the School of Diplomacy (Zonghengjia) in Chinese history. Together with Su Qin, he is known as "Su and Zhang". He was primarily active during the reign of King Huiwen of Qin. Relying on his outstanding diplomatic eloquence and strategy, he laid a solid foundation for Qin's "eastward expansion beyond the Hangu Pass". Zhang Yi's core political proposition was "Lianheng" (Horizontal Alliance), which involved persuading the six states to serve Qin individually, thereby breaking the "Hezong" (Vertical Alliance) among the six states, assisting Qin in defeating them one by one, and ultimately leading to unification.

Core Knowledge Points

* School of Diplomacy Thought: Zhang Yi was the epitome of the "Horizontal Alliance" strategy. He believed that the six states were individually weak and could only ensure self-preservation by relying on the powerful Qin. In reality, this was a method to divide and weaken the six states' relationships, diminishing their ability to combine forces against Qin.
* Deceiving Chu for Land: The most famous diplomatic event in Zhang Yi's life was "Promising Chu 600 Li of Shangyu Land". He tricked King Huai of Chu into breaking ties with the State of Qi, promising to cede the Shangyu region. After Chu broke ties, he only acknowledged "6 Li". This move caused Chu to lose its ally and suffer a heavy defeat by Qin, marking the turning point from Chu's prosperity to decline.
* Assisting King Huiwen of Qin: After entering Qin, Zhang Yi gained the deep trust of King Huiwen and was appointed as Prime Minister. Through diplomatic means coordinated with military actions, he established Qin's hegemonic status in the mid-Warring States period, paving the way for the unification cause of later rulers such as Duke Xiao of Qin and Qin Shi Huang.

Connection with the Content of Zizhi Tongjian

As China's first chronological universal history, Zizhi Tongjian (Comprehensive Mirror to Aid in Government) begins with the Warring States period (the 23rd year of King Weilie of Zhou). In this historical narrative, Zhang Yi's activities are an important early chapter of the entire book.

1. Witness to Historical Turning Point: Sima Guang detailed Zhang Yi's persuasion process in Zizhi Tongjian, aiming to show how the game among the states shifted to "Qin Dominance" after the decline of the Zhou royal family. Zhang Yi's diplomatic maneuvers were a key turning point for Qin's transition from a border state to a unified empire.
2. Reflection of "Zizhi" Perspective: The book's evaluation of Zhang Yi is not merely praising his wisdom, but objectively recording the consequences of his strategies. Through cases like Zhang Yi "Deceiving Chu", Sima Guang warns future generations about the importance of diplomatic integrity and the lesson that excessive use of scheming can lead to a bankruptcy of national credibility.
3. Narrative Focus: In Zizhi Tongjian · Zhou Ji (Annals of Zhou), Zhang Yi's words and deeds occupy a large portion of the text. This reflects Sima Guang's view that diplomatic struggles in the Warring States period were as important as military wars. Zhang Yi's "Horizontal Alliance" strategy directly influenced the political landscape for hundreds of years to follow.

In summary, Zhang Yi was not only a prominent figure in the Warring States period but also an important case study in Zizhi Tongjian for interpreting power games and the rise and fall of history.