We must use time as a tool, not as a crutch.  John F. Kennedy

The irimi and tenkan, or as some say, omote and ura versions of techniques can be thought of as being suitable for different situations. For example, if uke pulls, tori could enter and perform an irimi type of technique. If uke pushes, then tori could perform a tenkan type of technique. Another way of looking at the difference is in terms of how tori leads uke's energy. In performing an irimi variant, tori is effectively returning uke's energy back towards uke and beyond. When performing tenkan, tori adds a little to uke's energy, initially encouraging it on, outwards, in the direction it was going, then redirecting. Yet another way of rationalising irimi and tenkan is in terms of time. Training with time in mind adds an air of reality to practice, yet training in timing is rarely specifically targeted in Aikido or other Japanese martial arts. Timing exists, of course, and it is learned unconsciously. Without a framework, however, many people do not actually know what it is that they know. Nor can they easily teach it. Some timing related concepts and exercises follow:

(a) Provoking the attack

Tori feints towards uke who responds by raising their own arm in defence. Tori then takes uke's raised arm and performs a technique. The initial feint is irimi in nature, but only if the body moves forward, as in an irimi type technique (if only the arm moves, it can not be called irimi; it is just a feint in Aikido). At this time, especially if uke stumbles back slightly, then tori can take initiative with an irimi movement. However, if uke responds a little more strongly preventing an irimi entry, then tori performs a tenkan movement.

A typical example of this timing is shomen-uchi ikkyo irimi, where tori initiates the attack and takes control as uke raises their arm in defence.

(b) Before the attack

It takes uke a short moment to invigorate and prepare their their energy for attack. Tori attacks before they are fully ready.

(c) As uke prepares for the attack (i)

As uke raises their arm in preparation for shomen-uchi, tori rushes in harmonising with the upward movement, then performs a technique. If tori's entry is quick and in harmony the result will be an irimi technique.

Tori rushes in just as uke has begun a shomen-uchi attack. It is almost a clash, but if tori catches it early enough uke will be overcome by a combination of tori’s forward momentum and the element of surprise - an irimi technique will likely result.

As uke begins to strike down with shomen-uchi, tori moves forwards quickly to meet it in the same time, and on meeting turns and deflects it slightly, adding energy to it. Tori typicaly moves ever so slightly to the side to avoid meeting the attack head on. Meeting at this slightly later point in time, uke's energy usually necessitates that tori perform a tenkan technique. However, while the initial movement is tenkan in nature, tori might decide to follow up with an irimi technique. While practising, Tori can have the feeling of starting late, catching up and overtaking, or, moving at the same time in direct co-ordination and total harmony with uke.

Total harmony with the attack occurs when tori harmonises with uke’s movement in both of the latter two phases. As uke raises for shomen-uchi, tori does likewise, as uke cuts, tori cuts too and makes technique by adding energy and redirecting. Here, tori harmonises with uke’s preparation and attack, a good starting point to master before altering the time. Strangely, the more one practises in harmony, the easier it becomes to change the time.

As uke cuts down with shomen-uchi, tori cuts up hitting uke’s strike at a tangent, contacting on or near the elbow and deflecting it slightly off course. Tori follows though with a new cut, adding energy to uke’s arm. If the follow up cut is fast, a tenkan technique will result, if slow and uke recovers slightly, irimi is natural. The feeling in the deflection is as if trying to knock something out of uke’s hand mid-swing.

That point in time after a powerful shomen-uchi or tsuki lunge where uke has momentarily over-extended themselves is another opportunity waiting to be taken. At this exact moment, uke is likely wide open for an incapacitating strike and adding a little energy to uke's direction of imbalance offers an opening to begin a tenkan technique.

(i) After the attack (ii)

After uke has over-extended it is natural to recover. In this instance, tori should immediately harmonise with uke’s retreat and move in for an irimi technique.

What is apparent then, is that the distinction between when one should, and when one should not perform an irimi or tenkan type technique can be based upon the time of meeting uke's energy. It should also be pointed out that it is possible to mix irimi and tenkan together. One can start with an irimi movement and finish with tenkan, and vice-versa, but not recommended in gradings where one is supposed to keep them separate to show that one does indeed know the distinctions. Of course, those keen to learn Aikido should be aware that the above distinctions are rarely, if ever, taught in any rational framework.

(j) Fencing time

All martial arts deal with timing but few appear to provide a clear structural framework of principles that embody timing as a principle unto itself. With a little imagination it ought not be too difficult to transfer Italian concepts of timing to any martial art. Even better would be to structure one’s own training to formally incorporate it.

Italian schools of fencing combine time with method to produce strategy. In fencing, one aggressive or one defensive movement is labelled as being done in one time, irrespective of the speed of the movement.

 dui tempo - double time: The simplest to understand and practice, but easiest to defend against. Here, block/parry and counter-strike make two completely separate movements.

mezzo tempo - middle time: Counter the attack as it develops, sometimes with the feeling of overtaking it.

in tempo - in time, or stop hit: Avoid and counter-strike in harmony with the attack, in the same time.

stesso tempo - one time: Intercept, deflect the attack, and counter all in the same time.

contra tempo – counter time: A counter attack is provoked, and exploited.

Of swordplay, George Silver (1599)[1] explains his four true times: (1) time of the hand, (2) time of the hand and body, (3) time of the hand, body, and foot, and (4) time of the hand, body, and feet. His four false times are: (1) time of the foot, (2), time of the foot and body, (3) time of the foot, body, and hand, and (4) time of the feet, body, and hand. Here it is interesting to note that Aikido, a body art whose motion originates in the centre, appears to be based on his false times.

Techniques without time are nothing more than dead form. Training in the tempo of movement is a priceless tool of strategy; one can anticipate and predict or lure to create the immediate future. However, it must be remembered that European fencing is a hand art whereas Aikido is primarily a body art. As such, Aikido offers a few more variations such as taking the balance, adding energy to the attack, and looking for openings in the midst of movement to a different range of target techniques. One thing to be wary of is that a lot of basic Aikido techniques are based on the simplest and most basic Italian concept, duo tempo. If one has the knowledge of where one is in time, one can modify it to be different. A sensible learning strategy is to isolate examples of various times within Aikido training and to memorise and practise them.