This is the strategic intention of treading on the point of your opponent’s sword with your foot. More precisely it is the intention of treading on the sword of your opponent with your left foot immediately before it stops when he swings it. If you take the initiative here with your sword, with your body and with your spirit, you can easily win.
Without this strategy an undesirable situation may develop, in which attack and counter attack constantly alternate. The movement of the foot can be slow. The opportunity to tread down a sword does not occur often.
Ponder this carefully.
To tread down the sword is to control it just as he stops his attack, as if he cuts right down and you stamp on the blade just as it touches the ground.
This is done mentally and physically with the body but not always with the foot, in fact it is more usually done with the sword. I have read this as one should tread on the spot where the opponent’s sword is about to fall. Since this would put you under the attacking blade I’m fairly certain this is not the correct way to think of this article. Rather one should arrive over the attacking sword just as (after) it gets there, not just before.
In the Go Rin no Sho Musashi explains this somewhat more clearly with his example of a large battle, where the bowmen fire their arrows. In this case the other side ought to be running toward the archers just as the archers have fired. If they do not the bowmen can get another arrow knocked and fire. On the individual side, if we stand with our opponent and trade strikes we simply go back and forth forever. Don’t trade blows, stomp on his sword.
Let’s examine the fifth kata, migi waki gamae where we do this twice, first with spirit, then with our sword. The first time we thrust at our attacker with the long sword from our right hand side to the center, this disrupts his balance just as he finishes his cut downward, and then we follow up immediately with kissaki gaeshi and a cut downward on his wrists. He is forced back and attacks again, this time we avoid by moving back and as he finishes his strike we trap his blade with our short sword, preventing him from lifting it again, and using kissaki gaeshi we strike his head with our long sword.
In jodo the perfect example of this would be monouchi. One stays in front of the opponent, providing a tempting target even as the defensive move is made, then one steps offline to avoid being hit and follows the cut down to strike the wrist of the attacker just as his sword stops. This movement would be the equivalent of starting our attack just as we hear the guns fire from the other side so that we are across the gap before the enemy can reload.
In aikido we slip to the opponent’s right side (his rear) just as he cuts down and we put our hand on top of his wrists just as he finishes his cut. From here we have many options while he is prevented from attacking further.