Japanese military communication in feudal times utilized various visual and audible signals including flags, banners, drums, and conch shells. Flags featured identifying mons and were used to denote military units. Drums were used to rally troops and set marching pace. Conch shells issued orders across the battlefield through a system of calls. Messengers also delivered coded messages to prevent enemy interception of communications.

1. COMMUNICATION
According to cross cultural analysts, Japanese
people often communicate with each other
without using words, heart-to-heart, like
telepathy. The Japanese call this “ishin
denshin”. It is more subtle, more indirect.
Saving face and not embarrassing people are
important.

2. COMMUNICATION

If you look at Japanese people in the metro or in
cafes, they do not seem communicate at all, unless
there is a process of long range telepathy. Most are
wired up to a Walkman and to listen to music.
Married couples do not see much of each other.
Against that young Japanese, especially girls, are
forever chattering away.

A recent BBC survey of more than 27,000 across 26
countries provides some interesting insights into
how the Japanese communicate. In short, Japan is
the nation which is the most hooked to the Internet.
Some 84 per cent say they could not cope without
the internet, and 94 per cent agree it gives them
more freedom.

3. MILITARY COMMUNICATION

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.

Flags and banners

Sashimono were small rectangular banners worn on the backs of
ashigaru, or common soldiers. They typically featured the mon of
their daimyo or clan, and used colors to denote units or divisions.

4. FLAGS AND BANNERS

Jirushi, various flags or banners used as a means of
identification. Hata-jirushi were one of the older types of
standards; they were long streaming banners attached to a
crosspiece and held up on a long bamboo or wooden rod.
Uma-jirushi ( 馬印 , lit. horse standard) were the massive,
often three-dimensional, banners used to distinguish the
daimyo or other top commanders on the battlefield. Sode-
jirushi, a badge worn on the shoulder armour, and kasa-
jirushi, a badge worn on the helmet, these were used in
place of the (more cumbersome) sashimono in night attacks,
ambushes, sea fights, and on stormy days. For private
soldiers they are used as regimental badges.

5. FLAGS AND BANNERS

Nobori ( 幟 , lit. flag, banner) are perhaps the most well-known of feudal
Japanese military flags. Introduced somewhat later than the hata-jirushi,
nobori were stiffened pieces of cloth, attached to a pole through loops, and
including, of course, a mon or other identifying mark on it, to represent the
samurai or daimyo who carried it.

The horo ( 母衣 ) were large pieces of cloth, not entirely unlike a cape or
cloak, which would be worn on the back, supported and shaped by a series
of bamboo or wooden sticks. In addition to displaying an identifying mon or
symbol, and making the samurai appear larger-than-life, it served the
purpose of arrow entangler. Ultimately, it marked that warrior as someone
important, usually a messenger or scout, and worthy of honorable treatment,
even by his enemies.

A daimyo would often signal with his war fan "gunbai or gunpai" as well.
While these fans were much larger than the usual paper or silk ones, it
seems unlikely that orders could be conveyed to thousands or tens of
thousands of warriors in this way.

Saihai were signal batons used by samurai commanders, these were small
hand held staffs with strips of leather, lacquered paper or a streamer of
animal hair on one end.

6. Messages and messengers

Communications were, of course, not only necessary on the battlefield,
but between battles as well. Takeda Shingen famously set up a system of
fire beacons across his Province of Kai, so that he could be notified in
the capital of Kofu as soon as his rival Uesugi Kenshin made a move.
Wooden towers were filled with combustible material, and as each
was lit, the next, some distance away, would see the signal and
light theirs.

Once an army was on the move, scouts were often sent to provide
reconnaissance, and messages needed to be transmitted between
elements of the same army, or between allies, speedily, and without
the information falling into the hands of the enemy. A number of
systems of protecting their intelligence, and ensuring its safe
delivery came about. Often, written messages would end with 'you
will be informed of these things by the messenger.' By not placing
the entire message in writing, the messenger could enjoy some
degree of protection from those who would kill him and steal the
scroll.

7. Messages and messengers

Attaching messages to arrows fired over a castle's
walls was a common method of communicating with
allies under siege. While the message was often
simply wrapped around and tied onto the arrow,
some used special arrows with hollow shafts
specifically designed for this purpose. Whistling-
bulb arrows, originally used just before a battle to
draw the attention of the kami that they should
watch the events about to transpire, were modified
to serve as message-carrying arrows.

8. Audible signals

Taiko are large Japanese drums which, in addition to their
military applications, are very common elements in rituals
and matsuri (festivals). In war, taiko would be used to rouse
the troops, calling them to battle, as well as to summon allies
onto the field, to set marching pace, and to encourage troops
as they approached victory.

Horagai were conch shells used as trumpets or horns, to
issue orders across the battlefield. A complex system of
conch calls came into use by the height of the Sengoku
period. Many yamabushi were renowned for their skill with a
conch, and were hired into feudal armies as kai yaku, or
trumpeters.