Duke Yin of Lu

Duke Yin of Lu (, died 30 November 712 BC), personal name Ji Xigu, was a duke of the Lu state, reigning from 722 to 712 BC. He is notable in Chinese history as being the first ruler of Lu whose reign was recorded by the Spring and Autumn Annals and, by extension, its commentaries such as the Zuo Zhuan, the Gongyang Zhuan, and the Guliang Zhuan.

Accession
After the death of Duke Hui of Lu in 723 BC after 46 years of reign, Prince Gui (軌), born to the late Duke's main wife, was to succeed to the throne. However, Prince Gui was young, so Prince Xigu, his elder brother born to a concubine, was installed to the throne with the tacit understanding that he would abdicate in favor of Prince Gui after he became an adult. The Zuo Zhuan points out that the Spring and Autumn Annals makes no mention of Duke Yin's accession in the entry for his first year of reign because Duke Yin was "acting as regent."

Reign
Duke Yin's reign began with creating goodwill with Lu's neighbors. In spring 722 BC, Duke Yin swore a covenant with the Viscount of Zhu at Mie (蔑). In the autumn of the same year, he swore a covenant with Song at Su (宿), which, according to the Zuo Zhuan, was Lu's first diplomatic contact with that state. The next year, in spring 721 BC, Duke Yin met with a Rong tribe at Qian (潛) to restore good relations during the reign of Duke Hui. The Rong asked to swear a covenant, but Duke Yin refused. However, Duke Yin eventually agreed to a covenant in the autumn of the same year, conducting the ceremonies at Tang (唐).

In 719 BC, Prince Zhouxu of Wey usurped the Wey throne by murdering Duke Huan of Wey, his elder brother. Soon after, in order to establish legitimacy, he forged an alliance with nearby powers Song, Chen, and Cai to attack Zheng, which had been on unfriendly terms with Wey for generations. After multiple expeditions in a year, in autumn, Duke Shang of Song sent an envoy to Lu to seek support. Though Duke Yin declined support, Prince Hui (翬; also known as Yufu - 羽父) reinforced the allied army with a force despite the Duke's prohibition. Later in the same year, Zhouxu's forces were defeated and, failing to garner support, Zhouxu was himself killed.

In spring 718 BC, Duke Yin planned to visit the fisheries at Tang (唐), a place near the Lu border. This attracted expostulation from an official named Zang Xibo, who remonstrated that "a ruler is the one who guides the people into the right paths and the proper usage of objects" and that the procurement of ordinary articles was "the affairs of menial laborers, and the duties of petty officers." Duke Yin departed for Tang anyways, but not without excusing himself by saying, "I will inspect the borderlands." Zang Xibo did not accompany him, claiming illness. Duke Yin showed contrition after Zang Xibo's death in the winter of the same year, saying, "My uncle was resentful of me, the unworthy one. I would not presume to forget that." Duke Yin granted Zang Xibo a posthumous promotion during his funeral.

In spring 713 BC, Duke Yin made an alliance with Qi and Zheng to attack Song at Zhongqiu (中丘). The attack began in the summer of the same year, the allied army taking multiple cities from Song.

In spring 712 BC, the Marquises of Teng and Xue (state) visited Duke Yin. They argued over their order of seniority, with the Marquis of Xue arguing that Xue was enfeoffed first and his counterpart of Teng arguing that he is a descendent of a high official of the Zhou court and the royal clan. Duke Yin arbitrated this dispute by sending Prince Hui to them to say that the descendants of the royal clan take precedence in meetings hosted by the royal clan, while, should he visit the Xue court, he would allow those of Xue's ruling clan to take precedence. The Marquis of Xue then agreed to have the Marquis of Teng take precedence.

In fall 712 BC, Duke Yin attacked the state of Xǔ along with Qi and Zheng. After a short siege, the capital of Xǔ was conquered, and its duke fled to Wey. Duke Xi of Qi intended to give the newly-conquered land to Lu, but Duke Yin declined, saying:"You, my lord, stated that Xǔ had not presented tribute, and that is why we followed you to chastise it. Xǔ already has submitted to punishment for its crimes. Even though you have issued a command, I, the unworthy one, would not presume to agree to what I have heard."The Duke of Qi then gave the land to Zheng instead. Xǔ would eventually regain its independence in 697 BC.

Death and Succession
In late 712 BC, Prince Hui offered Duke Yin to kill Prince Gui so that he may take the throne once and for all in exchange for a high governmental position. Duke Yin refused, so, fearing that his plot may be revealed, Prince Hui went to Prince Gui and offered to murder Duke Yin for him instead. Prince Gui agreed, and so Prince Hui sent brigands to the house of the head of the Wei (寪) clan, in which Duke Yin had been fasting for a sacrifice, and assassinated Duke Yin. Prince Gui succeeded him to the throne of Lu and would become known as Duke Huan of Lu. Later, Prince Hui framed the Wei clan for the murder and killed some of its members.