Sasaki Kojiro was a famous swordsman who studied under Toda Seigan, founder of Chujo ryu, acclaimed at the turn of the 17th century for their Kodachi (shortsword) techniques. As partner to Toda Seigan, he became very proficient with the katana, eventually leaving the school and starting his own school, Ganryu (“The School of Rock”).
Sasaki Kojiro is most remembered for his duel with Miyamoto Musashi. At the time, Kojiro had become the swordmaster for Lord Hosokawa by age 18. He was particularly well known for a particular technique that he named tsubame gaeshi.
Now, tsubame gaeshi is a popular name for several different actual techniques that vary according to the different modern day ryuha (schools), so you should not confuse Sasaki Kojiro’s version with the modern one. The book, Miyamoto Musashi: His Life and Writings¸ tries to trace the technique from both the viewpoint of what Kojiro may have learned from Chujoryu, and from other historical sources:
The meaning of the name tsubame gaeshi can translate to either “to turn the sword at the speed of a swallow”, or “the sword that cuts the swallow”. They both imply very rapid turning of the sword. Kojiro was said to practice cutting swallows in half as they flew past a bridge. These agile little birds can turn very rapidly when they see movements, so the technique required quick changes in direction to cut the target.
From historical sources, the cut begins with a cut from above all the way to the ground. Then a second cut from the bottom upwards, with a very fast change of direction midway still cutting upwards.
The Ryuseiken version of tsubame gaeshi is close, but not entirely. There is a kesagiri first, and then a kiriage. However, the kiriage is followed by a suihei (horizontal cut) rather than cutting upwards, which I would assume is a kiriage but in the other direction. Kojiro’s tsubame gaeshi would seem to be kesa-giri, kiriage, and then immediately the opposite kiriage. He supposedly did this against a tiny target (a swallow) as it was flying past quite rapidly, but I’ll assume only one cut actually needed to connect. It was a matter of speed. Our tsubame gaeshi is also a matter of speed but it is relatively easier and not as tightly focused on a single spot.
The nature of our modern day tsubamegaeshi against a goza target includes the need for speed by cutting the target twice before it falls. However, even this technique is considered quite advanced. In Ryuseiken at our dojo, we don’t expect people will be able to perfect this technique against a single target (i.e. do it about 90% of the time) until sandan. In other styles I have seen, it is something that only yondans and higher should attempt.
Given that Kojiro was one of the best of his time, I’m not surprised that his version is much more difficult to accomplish. Even if it has changed over time, it’s great to see the element of extreme speed is still there.