1: Why I call this way the two swords.
(translation of articles from Machida, Terao: Bull Nippon Sport Sci Univ 42(2) 165-179, 2013)
Musashi had his students train by holding two swords, one in each hand. This way the left hand became less important and the students learned how to use a sword in one hand.
If you’re riding a horse, wading through a swamp, carrying something in one hand, it is of some considerable value, when in battle, to know how to use your sword one handed.
It may be hard at first, but as with anything if you practice you will eventually build the strength and the skill to do it. Of course it is also important to pick a sword that is a good weight for you.
Musashi taught his students to use nito, two swords, in order to force them to use them one handed. That seems fairly obvious. What may not be so obvious to anyone who has not tried this is the amount of coordination by the two sides of the body needed for his kata. The two hands are not doing the same thing, they are almost completely asymmetrical in both their movements and their timing. This has led people to belive that Musashi was ambidextrous. Perhaps he was, but one can certainly become more ambidextrous by working with a sword in each hand. In fact it’s not a bad idea to learn a new skill with the left hand, since neither has an advantage.
People often wonder why Niten Ichiryu bokuto are so thin and light. The answer is fairly simple, holding two bokuto out at arms length in front of you for hours at a time is hard. If you were to try doing it with regular bokuto you would damage your shoulders, and what’s the point of that if you’re a soldier. The idea is to build your strength and skill step by step rather than in a crash course. Strength built up slowly is resilient, the ligaments and tendons go along with the muscle, the mind gets used to the power. Compare the high school bodybuilder with steroids, protein shakes and heavy weights to the life-long fisherman. The kid may look bulky and strong but put him on a boat for 5 hours at 3am and then make him haul cold nets for another 5 hours and see how he does. Toughness counts more than strength and much more than bulk.
I sell iaito and I’m occasionally asked by youngsters if I can supply one that’s as heavy as a “battle ready blade”. Sure I can, most of them are heavy and, if not overweight, overbalanced. Such blades are a delight to sell because I know I’ll sell another in a couple of years to that same kid who now has tennis elbow.
If you’re going into battle you may want a blade that isn’t going to fail and that has some heft to it. That battle may last a day or two. If you’re going to train for four hours a day for your entire life you need to use a blade that suits that training. You need to have a light, well balanced sword that will not hurt you.