Xi 檄, also called xiwen 檄文, xishu 檄書, junxi 軍檄 or lubu 露布 "proclamation", translatable as "dispatch, summons, warning proclamation or call-to-arms", is a special type of imperial order, and also a literary genre. The Classics commentary Jingdian shiwen 經典釋文 from the Tang period 唐 (618-907) once said (not included in the transmitted version), xi were "military documents" (junshu 軍書). The dictionary Shuowen jiezi 說文解字 adds that they were usually written on bamboo slips with an extraordinary length of 1.2 or even 2 chi 尺 (see weights and measures) and used to give orders (yong yi hao zhao 用以號召). Urgent documents were marked with feathers and were therefore called “wing dispatches” (yuxi 羽檄). The earliest mentioning of a military dispatch is found in the history book Shiji 史記 where the strategist Zhang Yi 張儀 (d. 310 BCE) is said to have informed the counsellor of Chu 楚 with the help of a dispatch. An even earlier case was King Mu’s 周穆王 (10th cent. BCE) order to Moufu, the Duke of Ji 祭公謀父.
It is known that during the Han period, military dispatches were used to launch attacks or threaten the enemy, to launch campaigns, instruct the troops, to appoint commanders or to call back victorious armies.
The literary aspect of military dispatches lies in the use of refined and adorned language, in a combination of simple and rhymed prose (pianwen 駢文). The use of rhymed prose in military dispatches begins with the Tang period 唐 (618-907) and finds outstanding examples (also in earlier times) in Chen Lin’s 陳琳 (d. 217) Wei Yuan Shao xi Yuzhou 為袁紹檄豫州 and Xi Wu Jiangxiao buqu 檄吳將校部曲, Zhong Hui’s 鐘會 (225-264) Xi Shu wen 檄蜀文, Sima Xiangru’s 司馬相如 (179-117 BCE) Yu Ba-Shu xi 諭巴蜀檄 or Luo Binwang’s 駱賓王 (c. 640-c. 684) Wei Xu Jingye tao Wu Zhao xi 為徐敬業討武曌檄 (also known as Dai Li Jingye zhuan xi tianxian wen 代李敬業傳檄天下文), Zhu Yuanzhang’s 朱元璋 (Emperor Ming Taizu 明太祖, r. 1368-1398) Yu Zhongyuan xi 諭中原檄, Niu Jinxing’s 牛金星 (d. 1652) Tao Ming xi 討明檄, Hong Rengan’s 洪仁玕 (1822-1864) Zhu yao xiwen 誅妖檄文 or Liang Qichao’s 梁啟超 (1873-1929) Yun-Gui xigao quanguo wen 雲貴檄告全國文.
Liu Xie 劉勰 (d. 522), author of the literary theory Wenxin diaolong 文心雕龍 (ch. Xi yi 檄移) provides an explanation of the term with a word-pun: “dispatch” (xi /ɣiek/ 檄 ) means “lucid” (jiao /kieu/ 皦; compare the right parts of the characters), however the word 檄 might originally just have been a word for the physical document, written on wooden slips. Though unembellished, its language was to be succinct and its narrative clear. “Its facts should be evident, its reason sound, its spirit high, and its language clear-cut" (transl. Shih 1959) by stressing the virtues of the own side and the depravity of the enemy.
In late imperial times, the word xi was also used to denote internal military communication or even such among civilian institutions.
The genre of xi is therefore often put side by side with the genre yi 移 "letter of dispatch, communication", leading to the expressions xi-yi 檄移 or yi-xi 移檄. To some extent, the two types of writing corresponded to each other, xi being used to denounce the enemy (shengtao 聲討) and order attacks (zhengzhao 征召), and yi to clarify facts (xiaoyu 曉諭) and blame the adversary (zebei 責備). The Wenxin diaolong explains this interaction in both the military and the civilian realm as xi being an address to the enemy (nidang yong xi 逆黨用檄), and yi directed to allies (shuming zi yi 順命資移). In the civilian realm, proclamations (yuxi 諭檄) served to pacify the people.
The word fu-xi 符檄 is a collective term for documents of the types xi, yi, and fu 符. Other combinations are zhao-xi 詔檄 (edicts and proclamations) or ce-xi 策檄 (memorials and proclamations).
The words shuxi 書檄 and zhangxi 章檄 are a general terms for communication documents.
The word jianxi 牋檄 (see jian 牋) is an occasional semi-public letter to functionaries of high rank.