郑国 / Zheng State
郑国 / Zheng State enters this branch through 《资治通鉴·周纪》07丨两起刺杀（1）, where 芮淇讲透资治通鉴 uses Zheng to explain both small-state diplomacy and internal political violence. The source says Zheng had once grown strong under Zheng Zhuang Gong, but its location between 晋国 and 楚国 left it exposed whichever great-power patron it chose.
In the episode, Zheng besieges 韩国’s Yangdi soon after 韩景侯 dies, then is itself besieged by 楚国 at Xinzheng after appearing to side with Jin. Internally, the killing of prime minister 子阳 and the later installation of 郑康公 by Ziyang’s faction make Zheng the source’s main example of the shift from rule-bound aristocratic politics to harsher Warring States power struggle.
《资治通鉴·周纪》07丨两起刺杀（2） completes that Zheng thread: 子阳’s remaining faction kills 郑繻公 and installs 郑康公. The same source later treats 负黍’s return from Zheng to Han as evidence that Zheng’s territorial control is weakening.
Connections
- Small-State Buffer Diplomacy / 小国夹缝外交 - main geopolitical frame.
- Spring-Autumn to Warring States Political Violence / 春秋战国政治暴力转型 - internal violence frame.
- 子阳, 郑繻公, and 郑康公 - Zheng factional-assassination branch.
- 韩国, 晋国, and 楚国 - pressure field around Zheng.
- 负黍 and Territorial Control Churn / 城池反复易手 - territorial-control branch.