北宋时阶级矛盾、民族矛盾都十分尖锐。国内, 农民起义、士兵叛乱此起彼伏;国外,契丹、党项等游牧民族军事进攻频仍,边境烽火不绝。因此,北宋王朝对军队的保密通信十分重视。军事通信是军队装备的重要组成部分之一,直接为军事行动服务。根据宋人曾公亮编纂的《武经总要》(前集)记载,宋军在战争实践中发明了一种类似于今天“密码”的军事通信手段,宋人称之为“字验”。为防止军事情报在传递过程中泄密,又使书写方便,宋军把战场上通常可能出现的军事情报分为40种:请弓、请箭、请刀、请甲、请枪旗、请锅幕、请 During the Northern Song Dynasty, class contradictions and ethnic conflicts were very sharp. In China, peasant uprisings and soldier rebellions came one after another; foreign nomadic ethnic offensive branches such as Khitan and Party members continued to frequent the war on the border. Therefore, the Northern Song Dynasty attaches great importance to the secrecy of the military communications. Military communications is an important part of military equipment and serves military operations directly. According to the records of the “Wu Jing Zong Yao” (the first episode) compiled by Song Gong Zeng Gongliang, Song Jun invented a means of military communications similar to today’s “password” in the practice of war. The Song people called it “word experience.” In order to prevent the leakage of military intelligence in the process of transmission and to facilitate writing, Song military divides the military intelligence that may normally appear on the battlefield into 40 types: Please bow, arrow, knife, please A, please gun flag, please pot ,please