Military Communication of Feudal Japan

A variety of methods were used to communicate across the battlefield in feudal Japan, much like in any other culture. These methods included visual signals like flags and banners and audible signals using drums and horns. Messengers on horseback used ciphers and other methods to prevent their messages from falling into the wrong hands. By the beginning of the Sengoku Period, battlefield communications had become fairly complicated affairs, with larger armies than ever before, and a multitude of flags and banners covered in a myriad of colors and designs.

Since the beginnings of what we would today recognize as Japanese culture, and probably earlier, various symbols, crests, banners, or markings on armor were used to help identify and distinguish warriors on the battlefield. The mon, or symbol, of a clan or a daimyo was particularly common, identifying which side a warrior fought on; some samurai used their own names or mon rather than that of their lord, while other factions, such as the Ikkō-ikki, could be identified by banners declaring namu amida butsu, praising the name of the Amida Buddha.

By the mid-16th century, flags and banners were seen in greater numbers than ever before, and in an unprecedented variety of styles, sizes, shapes and colors. Where once only higher-ranking samurai and commanders had standards (flags), now lower-ranking warriors wore flags to denote their unit or division, along with their clan or lord. Not only were armies larger than in the past, but the number of clans present on any given side in a battle had increased as well. In any one battle, a single daimyo could have under him several other daimyo, each with a number of units or divisions, and sub-commanders, as well as individual samurai of such a reputation (or wealth) as to warrant their own individual banner. This profusion of banners meant that the commanders, especially the daimyo at the head of each side of the battle, had to have especially large and noticeable standards to identify their location; warriors needed to know where to rally around, whose orders to follow, and what those orders were. The role of standard bearer was one of the most dangerous, and thus one of the most honorable, positions on the field of battle.

Every culture has used drums, horns, or other audible signals to announce the call to battle, to set marching pace, and for a number of other basic commands. Before the age of radios, telephones, and computers, this was more or less the only way to issue orders to a large group of people.

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