Iaijutsu and iaido are components of kenjutsu 剣術, the arts of the sword. Iaijutsu, iaido are specific techniques used to draw the sword from the saya (sheath). It is also called battōdō or battōjutsu抜刀術.
The suffix of jutsu 術 means techniques or the art of. Batsu 抜 or nuku means to pull. Battōjutsu means the art of pulling out the sword.

Iaijutsu, on the other hand, has a different connotation than battōjutsu. Iai 居合 is made up of two characters, the first I 居. This character means to be or exist and also has a broader meaning of sitting. The second character, ai 合 means to meet or unite or join.
There is no direct translation into English of Iai. The art of using the sword in everyday situations is probably the best way to think of it. Iaijutsu does not mean the seated forms solely. There is also standing, which is called tachi-iaijutsu 立居合術.
Origin

No single person can claim the title of the creator of iaijutsu. Although bushi such as Iizasa Choisai Ienao of Tenshin Shōden Katori Sintō-ryū (14th Century) and Hayashizaki Jinsuke Shigenobu of Shin Musō Hayashizaki Ryū (16th Century) significantly contributed to its spread and popularity within koryū.
Iaijutsu and iaidō are done from various postures from seated to standing. Although the character 居 has the older meaning of sitting, iaijutsu contains the feeling of being at "rest" in a non-battlefield situation and is more relating to that of everyday life. Sitting in a meeting, or having a meal or being served tea, etc. etc. Walking down the street is a part of this "existing in everyday life" idea.
Iaijutsu is concerned with the art of using the sword from its rested position in the saya. The person studying iaijutsu learns to deploy the sword for somewhat defensive purposes. In Japanese swordsmanship, these defensive techniques also include acts of getting the sword out to attack as well. Iaijutsu is not purely defensive action. Methods for stealthy or covert attacks are also included in many systems of iaijutsu and iaido.

In general, the sword is worn through the obi (belt) with the cutting edge facing up. Starting around the sixteenth century the sword was easily worn through the obi and hakama since many more samurai were not dressed in armor. The sword placed in the obi and straps of the hakama became normal usage. Earlier the sword was worn in a method known as tachi. It with the cutting edge facing downwards. It was suspended by two cords affixed to the saya. It hung much lower than the more modern version of it being in the obi. Having the cutting edge face down in tachi style also puts the handle at a convenient level to draw the sword. Wearing the sword in the obi with the cutting edge facing downwards creates an awkward method of drawing.
The swords (tachi) had also changed more into the katana we know today. The advent of a change in political climate, wardrobe, and utensils such as the uchigatana and katana paved the way for the advent of iaijutsu. The samurai needed a method to use the sword in a different environment.
Forms
Iaijutsu and iaido are done from crouched (iaigoshi), kneeling or semi-sitting (tatehiza), formal sitting (seiza), regular sitting (agura) and standing (tachi) postures. The sword might be in the obi, or it might be on the floor to either side of the practitioner. It might also be done carrying the sword in one hand. There is a myriad of ways different schools approach the art iaijutsu in swordsmanship. The handle (tsuka) and sheath (saya) and sword guard (tsuba) are also used as weapons in some schools in their iaijutsu techniques (waza). Iaijutsu can also contain grappling within its techniques. It is not uncommon to use a kick or a punch or joint locks within the iaijutsu techniques.
©2018 S.F.Radzikowski

ラジカスキー真照
館長Saneteru Radzikowski is the head sword instructor of Shinkan-ryū Kenpō. He lives and teaches Iaijutsu and Kenjutsu from Nara, Japan.
You With Sword In Hand, Calm Yourself
The mental issues involved with subscribing to someone you dislike, hate, have anger towards, desire...
Greed And Martial Arts
We must endeavor to cultivate generosity while looking at the roots of our greed. Removing...
Kesagiri: Anatomy of A Sword Strike
In Japanese swordsmanship, there have been many hundreds of schools. There are, however, only a...
Seven Points For Learning Martial Arts
I am often thinking about how to learn bujutsu productively. The efficiency of body and...
Pain & Training In The Martial Arts
Pain & Training Pain is a universal dilemma. Especially for those in sports or martial...
Reflections on 31 Years of Martial Arts and 8 Years of Shinkan-ryū Kenpō
不動心 (Fudōshin) – The Immovable Mind As I mark 31 years of practicing martial arts...
Cómo aprender Kenjutsu?
Aprender cualquier cosa tan profunda como un arte marcial requiere de un maestro. El kenjutsu,...
How to self-learn sword skills?
How to self-learn sword? A question that pops up in my communications frequently is, “How...
Unleash the Potential of Your Iaido Success
We’re diving deep into the art and discipline of Iaido, a journey that goes far...
Guilt and Responsibility
I heard a student say, “If I don’t do any kind of training every day,...
Teaching yourself Iaido and Swordsmanship
The Challenges of Self-Learning Swordsmanship In martial arts, particularly in the study of swordsmanship, a...
Koryū Menkyo Kaiden & Classical Martial Arts Proliferation
免許皆伝 Menkyo Kaiden and Koryu Proliferation Mention menkyo or menkyo kaiden around some martial artists...
Munen Muso And Mushin The Warriors Mind
What is the difference between munen and mushin? These concepts outline the ideal mental state...
Four Enemies
Four Friends. Four Enemies. One morning while on alms rounds the Buddha gave a heap...
Budo Thoughts: Practice is life.
Practice is life. Life is practice. Enjoy them together. Enjoying morning keiko outdoors. The smell...
Bushido: The Soul of Japan
The code of the samurai is always popping up in martial arts circles and popular...
Too Many Martial Arts
The koryū of Japan are not self-defense arts. Although they can be authentic and certainly...
Duping The Gaijin – Martial Arts Fraud
Some Japanese schools or individuals wish to capitalize on the ignorance of non-Japanese martial artists...
Bushido Chūgi The code of Loyalty
Loyalty is one of the shining points in any list about the virtues important to...
Saya no uchi
I train to strike correctly. I perform keiko to understand the angles of my sword....
The Martial Arts Heart
Budo values reflection and compassion. When these are not present it is hard to develop...
Advance The Sword And Mind
No matter what, move. Advance. Unceasingly against whatever odds, internal or external, move towards the...