燕惠王後悔使騎劫代樂毅,以故破軍亡將失齊;又怨樂毅之降趙,恐趙用樂毅而乘燕之弊以伐燕。燕惠王乃使人讓樂毅,且謝之曰:"先王舉國而委將軍,將軍為燕破齊,報先王之讎,天下莫不震動,寡人豈敢一日而忘將軍之功哉!會先王棄群臣,寡人新即位,左右誤寡人。寡人之使騎劫代將軍,為將軍久暴露於外,故召將軍且休,計事。將軍過聽,以與寡人有隙,遂捐燕歸趙。將軍自為計則可矣,而亦何以報先王之所以遇將軍之意乎?"樂毅報遺燕惠王書曰:
臣不佞,不能奉承王命,以順左右之心,恐傷先王之明,有害足下之義,故遁逃走趙。今足下使人數之以罪,臣恐侍御者不察先王之所以畜幸臣之理,又不白臣之所以事先王之心,故敢以書對。
臣聞賢聖之君不以祿私親,其功多者賞之,其能當者處之。故察能而授官者,成功之君也;論行而結交者,立名之士也。臣竊觀先王之舉也,見有高世主之心,故假節於魏,以身得察於燕。先王過舉,廁之賓客之中,立之群臣之上,不謀父兄,以為亞卿。臣竊不自知,自以為奉令承教,可幸無罪,故受令而不辭。
先王命之曰:"我有積怨深怒於齊,不量輕弱,而欲以齊為事。"臣曰:"夫齊,霸國之餘業而最勝之遺事也。練於兵甲,習於戰攻。王若欲伐之,必與天下圖之。與天下圖之,莫若結於趙。且又淮北、宋地,楚魏之所欲也,趙若許而約四國攻之,齊可大破也。"先王以為然,具符節南使臣於趙。顧反命,起兵擊齊。以天之道,先王之靈,河北之地隨先王而舉之濟上。濟上之軍受命擊齊,大敗齊人。輕卒銳兵,長驅至國。齊王遁而走莒,僅以身免;珠玉財寶車甲珍器盡收入於燕。齊器設於寧台,大呂陳於元英,故鼎反乎室,薊丘之植植於汶篁,自五伯已來,功未有及先王者也。先王以為慊於志,故裂地而封之,使得比小國諸侯。臣竊不自知,自以為奉命承教,可幸無罪,是以受命不辭。
King Hui of Yan later regretted sending Qi Jie to replace Yue Yi, since this had caused the army's destruction, the loss of the commander, and the forfeiture of Qi. He also resented Yue Yi's defection to Zhao and feared that Zhao would use Yue Yi to exploit Yan's weakness and attack. King Hui therefore sent a messenger to reproach Yue Yi, while also offering conciliation: "The late king entrusted the entire state to the General, and the General shattered Qi for Yan, avenging the late king's enmity — there was none in All-Under-Heaven who was not shaken. How could I dare forget the General's merit for even a single day! But the late king passed away, I had just come to the throne, and those around me misled me. When I sent Qi Jie to replace the General, it was because the General had been long exposed to hardship in the field, and I wished to recall him for rest and consultation. The General listened to false reports and believed there was a rift between us, and so abandoned Yan for Zhao. The General may have acted in his own interest, but how does this repay the spirit in which the late king treated him?"
Yue Yi sent the following letter in reply to King Hui of Yan:
"I am without talent and could not carry out Your Majesty's commands in a way that satisfied those around you. Fearing I would tarnish the late king's discernment and damage Your Majesty's sense of honor, I fled to Zhao. Now Your Majesty sends someone to enumerate my faults. I fear that your attendants do not understand why the late king favored me, nor do they grasp the spirit in which I served the late king. Therefore I presume to reply in writing.
"I have heard that a wise and sagely ruler does not use stipends to favor his relatives — he rewards those with the greatest merit and places those whose abilities fit the task. Therefore a ruler who examines ability and confers office is one who achieves success; a man who judges conduct and forms friendships is one who establishes a name. I observed that the late king had ambitions that transcended his era, so I borrowed credentials from Wei and presented myself for inspection in Yan. The late king elevated me beyond my worth, placed me among the guests and above the ministers, and without consulting his kinsmen, appointed me Vice Chancellor. I did not presume to understand my own worthiness — I simply believed that in following orders and accepting instruction I might hope to avoid fault, and so I accepted the appointment without declining.
"The late king commanded me, saying: 'I have a deep accumulation of resentment and anger against Qi. I do not measure my own weakness, yet I wish to make Qi my concern.' I replied: 'Qi still has the legacy of a hegemon state and the heritage of its greatest victories. Its troops are seasoned and its armies practiced in war. If Your Majesty wishes to attack it, you must plan it with All-Under-Heaven. And to plan it with All-Under-Heaven, nothing is better than securing an alliance with Zhao. Moreover, Huaibei and the former Song territories are what Chu and Wei desire. If Zhao agrees and four states are pledged to attack, Qi can be utterly shattered.' The late king agreed, furnished me with credentials, and sent me south as envoy to Zhao. I returned with a completed mission, and the army was raised to strike Qi. By the way of Heaven and the spirit of the late king, the lands north of the Yellow River rallied to him as he marched to the banks of the Ji. The army at the Ji received the order to attack Qi and dealt them a devastating defeat. Swift troops and elite soldiers drove straight to the capital. The King of Qi fled to Ju, barely escaping with his life. Pearls, jade, treasure, chariots, armor, and precious vessels were all seized and sent to Yan. Qi's ritual bronzes were displayed in the Ning Terrace, the Great Lü bell was set up in the Yuanying hall, the ancient cauldrons returned to their rightful place, and the plantings of Ji Hill were transplanted to the banks of the Wen. Since the time of the Five Hegemons, no ruler had achieved a feat to match the late king's. The late king felt content in his ambitions, so he divided land and enfeoffed me, allowing me to rank with the minor lords. I did not presume to assess my own worth — I simply believed that in following orders and accepting instruction I might hope to avoid fault, and so I accepted without declining."