Zanshin, it is a concept found in Zen and Budo and is a state of mind where you are totally emerged at the present moment. It is a state where you are completely aware of your environment and your surroundings.
An Aikidoka state of mind is that it is always prepared and alert for any possible danger from all sides and multiple attacks from in front, both sides and behind in any situation. So when training you should never train in just one format of one person and one direction as attacks and multiple attacks can come from all directions and catch you off guard.
At all times during training you must maintain a relaxed but aware and alert state. This is regardless of what has happened so far. It is irrelevant if you are starting or near the end of class. It is irrelevant if you are performing a technique of throwing or pinning a person at any point, it can also be said it is irrelevant if you are winning or losing at something, Zanshin remains switched on in a natural state.
Interestingly, Zanshin in Japan is also an important component of the tea ceremony as when putting away each utensil; one should do so with the same emotion as when parting with a lover. The essence of Zanshin is giving both a discarded tool and the next utilised one the equal amount of attention.
Zanshin in a Martial Art perspective is based on the concept of Ki (Energy) through which one can feel the intention of the enemy or attack, which allows you to react more effectively, even to act before the opponent makes a move. This is not a supernatural power but is achieved through all your natural senses of Sight, Hearing, Smell, Taste, Touch and Movement/Balance and translated very quickly to your brain. The trick is to learn from these senses.
It is safe to say as humans we have evolved and lost or don’t use our natural Zanshin to a degree. If you observe any animal or insect they have all the Zanshin and reaction capability superior to man - given that they are not cluttered with thoughts or by evasive strategies. As humans we must train ourselves again in serious practice and a continued state of mental awareness and physical alert readiness beyond the dojo walls and into daily life. I’m sure you have felt Zanshin in the past but not been aware of it, when you walk into a room and you get a strange feeling something is about to happen before it does, be it a physical fight, argument or bad news.
When training in Aikido, Zanshin goes beyond a thought of your posture and focus after the execution of the technique. In class, the Sensei might say, “Don’t forget Zanshin” when the student absentmindedly walks away from the ending of the technique pleased with themselves as they have switched off with there glee, this training is to gage who and what is around you as an animal naturally does, at all times, using all your senses.
There are many stories of the founder of Aikido, Morihei Ueshiba - if you wish to dismiss them as Chinese whispers or exaggerated tales of the past or totally true, there are many people who stated the founder oozed Zanshin 24hrs a day as he was challenged by other martial artists, boxers, sumo wrestlers, and sometimes attacked unexpectedly by those who hoped to catch him off-guard and never could - earning the name of "O’Sensei" or "great teacher." because of this.
A person, at one time of training in my Aikido life, which I’m sorry to say I can’t remember who or where I was at the time, likened a physical form of Zanshin to ringing a bell. When it is hit, it rings for a period of time changing sound and pitch until it fades away, the sound may have stopped and faded away but the sound of what just happened remains in your head - the awareness of a bell sound. The sound and pitch, until it fades away, also acts as a level guide of danger and safety till all goes quiet of alertness.
However you see the explanation of Zanshin, it can only be attained by retraining your feeling of body and mind and through good Aikido practise.
“Many enemies surround me, thinking of them as one I do battle."