Five things you can learn from a Ninja

What are the skills a ninja needed to succeed in their role as a spies and warriors? One important work known as the Bansenshukai can tell us about their ‘art of war’, which includes some unusual tricks and tips.

Often considered mysterious and dangerous, the ninja of Japan are sometimes the product of legend more than history. There are only a handful of works that are focused on ninja, also known as shinobi. One of them is the Bansenshukai, written by Fujibayashi Yastuke in 1676. Fujibayashi wrote it during a period when Japan had seen decades of peace, and his concern was that the techniques and practices of ninja were becoming lost.


The Bansenshukai, which translates as ‘A Myriad of Rivers Merging into One Ocean,’ is very much a military manual, focusing on espionage and clandestine warfare. Various sections detail things like infiltrating a castle, carrying out night attacks, and using lock-picking tools. Some of these instructions involve more unusual situations. Here are five of our favourites:

How to tell if someone is fake snoring

When infiltrating a building at night, the ninja will often encounter people who are sleeping. The Bansenshukai offers several points on sleep patterns, noting that in certain seasons people tend to sleep more deeply, but this could also be affected by an individual’s weight or age – “younger people have so much energy that they ‘sleep tight’ in the dead of night or even later into the morning.” Even being happy or worried will impact one’s sleeping, the text notes.


Still, a ninja must be careful to listen to how people sleep and to understand what noises might indicate they are awake. Fujibayashi also includes a section on determining whether or not someone is pretending to snore:

Fake snoring sounds false and high-pitched and is regular in length and loudness. also, you can hear individual breaths between fake snores. If you listen carefully for a while, you will hear the person swallow saliva or sigh or draw a long breath. on top of that, he will try to move himself with as little sound as possible, his body, bones or joints will squeak. you should be aware of these points.

If you are still not sure if someone is really sleeping, the Bansenshukai advises scattering a light powder or ash on them or using a blowpipe to hit them with a single grain of rice.

How to learn which way is north and south

The Bansenshukai includes several sections on determining what time is it, or where you are. This is much harder at night time, especially if it is cloudy or gloomy. While the text first advises you to bring a compass, if you do not have one, then it gives instructions on creating the ‘south-pointing fish’:


Cut a fish shape out of thin iron leaf to the measurement of two sun in length and five bu in width and with a pointed head and tail. Then heat this iron leaf fish in a charcoal fire until it becomes red hot, then take it out by the head with iron tongs and place it so that its tail is in the direction of north. In this position it should then be quenched in a basin of water, so that only its tail is submerged and up to several tenths of an inch. This fish is then kept in a tightly closed box. To use it, fill a small bowl with water and set it up in a sheltered area, then the fish is laid as flat as possible upon the water’s surface, so that it floats, whereupon its head will point to the direction of the south.

How to cross a river

A ninja will need to travel across all types of terrain and will come along various natural obstacles. When coming to a river, the Bansenshukai gives advice on determining if it is deep or shallow, and how tides and flooding might affect it. With some rivers, a makeshift bridge can be built to cross them:

Use this if the river is not very wide, but is too deep for footed warriors to cross over easily. Heap stones in the shallows of your side, cut and gather wood or bamboo, or break down any houses nearby and take their wood. Lay three beams across the river and on top of the stone foundation, one in the middle and two on either side, and then tie many rungs at intervals to make it secure. When the bridge is long enough for you to walk out to the center of the river, you should tie three jakago long baskets to lengths of rope, then float these baskets on the upstream side of the bridge and maneuver them into position on the opposite bank; do this by using the downward flow of the river. Next put stones in the baskets so they form a foundation for the opposite end of the bridge.

A Japanese depiction of a ninja from 1853. Wikimedia Commons

How to figure out a password

Entering an enemy camp or base is one of the most challenging aspects of espionage. The Bansenshukai offers a section on the art of passwords, as it was a common practice in Japanese armies to use them as a way of guarding who could enter their areas.

The text explains that the typical method of protecting a camp would have the guards speak a word and then the visitor reply with a password. The ninja needs to discover this password, the easiest way of which is to talk with soldiers or labourers who might know it. “Nothing is better than talking to lower people to have them give away their secrets,” the text explains. “Particularly, the young, the drunk or the rash are best.”

If you cannot discover the password, then you can try guessing them. Fujibayashi found that the initial word is often connected to the password, so he gives a list of possible ones to try. For example, ‘forests’ go with ‘mountains’, ‘village’ with ‘woods’ and ‘water’ with ‘valley’. How you say these passwords is important too:

It would be better for you to answer in a way where you look careless because there’s always a possibility that it may be a different password. If you give your answer without being timid… then you will be able to get through the situation. However, the enemy may have an extra sign, such as one person picking his ear and the other person blowing their nose in response, and in such cases sometimes you should not rush into saying a password in response. To deal with such a situation, it is good for you to transform your appearance and pretend to be an ignorant lower soldier who would forget such things. In a military way of life, which is budo, there exists only danger. Therefore, you should have a calm mind when you face such an emergency.


How to carry a decapitated head

The taking of heads was one important aspect of medieval Japanese military culture. It was used as a sign of victory and to showcase one’s prowess. The Bansenshukai acknowledges this and offers advice on how to attach a decapitated head to your horse:

On one end of a cord measuring two shaku five sun, you should put a hook which is as sharp as a needle for making tatami straw mats. Pierce the head with the hook and attach it onto the rear shiode saddle horn or ring. Another way to attach a head is called oitsuke or ‘adding another head’ and is attached onto the rear left saddle horn or ring. When you are feeling ambitious and want to fight more, you should cut off the nose of the head before you attach it to the horse.

There are a lot more interesting pieces of advice found in the Bansenshukai. It has been translated by Antony Cummins and Yoshie Minami in The Book of Ninja, which was published by Watkins in 2013. You can buy it from