When the opponent attacks with his sword at close distance, it is possible to knock it away with your own sword, to parry or to hit.
The impact as opportunity means that this knocking away, parrying or hitting should be seen as an opportunity to a subsequent strike. All counter measures are intended to strike the opponent, whether it is by dominating the striking sword of the opponent from above, or by evading it, or by making it ineffective with a stroke of your own sword; body, spirit, and sword should always be prepared to strike.
This should be carefully considered.
Keep your eyes on the prize. You may need to shift position, block, deflect, or any of a dozen other movements throughout the fight, but you must never lose sight of the goal which is to strike down your opponent. In all things you do, you must feel as if you have linked that thing to the ultimate cut. If you step back and deflect from below you must continue back in and strike your opponent. This is suriage men from Kendo. If your two swords are in gedan and you must stop a strike to your head, do it with your shoto and cut his wrist with your tachi in the same motion. This is the final movement of the first nito seiho kata.
This may seem painfully obvious, but it is easy to lose sight of our goals. In a kata we may get all caught up in which foot goes where or just how fast to move from point A to point B. The goal is to study your opponent, not to dance as if you are alone on a stage. If you are looking for an answer on the world wide net you may surface four hours later wondering what it was you were looking for. Only discipline can keep you from dropping down a rabbit hole and getting lost.
Your normal life may not contain goals quite as obviously important as surviving a sword fight but you will find many situations each day where keeping your goal in mind will help you to progress. We talked of fixing the roof of our house. No matter how many jobs need to be done before we can get onto the roof, we must keep in mind that the roof needs to be fixed, otherwise our attention wanders and we become involved in less important work. Each job along the way must be considered part of fixing the roof, not as a separate piece of work.
Look once more at the title of this article. “The impact as opportunity”. Musashi is speaking of something a bit beyond setting up a series of events with an ending. This is not a set of episodes on TV or chapters in a book which are units in their own right. We are talking ippyoshi, all at once. In the Go Rin no Sho Musashi calls this the “hit at the edge” and he reverses the situation. There he speaks of us striking and the opponent blocking or deflecting our sword. In that case we look to cut anything that presents itself to us. If he does suriage (a rising brush of our sword to deflect it) we cut do (the side) before he can cut our men (head). He will perhaps lift his sword from gedan and hit our sword on the omote side (the left side from our viewpoint). Our sword drifts away from his head to our right. You will probably be right foot forward so you can twist your hips strongly to your left as you feel the impact. This will bring your sword back into the opponent on his shoulder, his ribs, his hip or his thigh. In this way you have redirected your sword without making a second movement. You have not hit the middle but you have hit at the edge. You have used the impact as opportunity.
Whether you have been deflected or you are deflecting, use that as an opportunity to strike.