Shimoto - Kato

…It re-emerged as one of the powerful nations during the Warring States period, adopted the Central Plains culture, and attacked Qi together with other nations in 284 BC, briefly taking control of most of Qi. However, it later suffered a counterattack from Qi and was also oppressed by Zhao. In 226 BC, Qin captured its capital, Ji, and it was destroyed in 222 BC. Spring and Autumn Period and Warring States Period [Michiharu Ito]
[Tsubame's Lower Capital]
During the Warring States period, the capital of the Yan state was called Xiadu, and its remains were discovered 2.5 km southeast of the county seat of Yi County, Hebei Province, in an area between the North Yi River and the Middle Yi River. Xiadu measures approximately 8 km east to west and 4 km north to south, and is divided into the Eastern and Western cities by a wall and a canal running north to south through the center.

*Some of the terminology that refers to "Shimoto" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…戦国時代に強国の一つとして再登場し，中原文化を採用し，前284年には諸国とともに斉を攻め，一時斉の大半を手に入れたが，のち斉の反撃をこうむるとともに，趙の圧迫も受け，前226年秦に都の薊を奪われ，前222年に滅ぼされた。春秋戦国時代【伊藤 道治】
［燕の下都］
　戦国時代，燕国の都城を下都といい，その遺構は河北省易県の県城南東2.5km，北易水と中易水に挟まれた地域で発見されている。下都の大きさは，東西約8km，南北約4kmで，中央を南北に走る城壁と運河によって東城と西城に分けられている。…

※「下都」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報