How did the ninja legend spread around the world?
It took on a life of its own very much in the 19th century in Japan and then spread to the West, but really after the Second World War. I blame James Bond, really. The Bond movie You Only Live Twice really popularized the idea of ninja among people who are not interested in martial arts. It’s quite strange, really: the idea of the ninja spread, but in the film they’re not represented as ninja at all, more as commandos. Nevertheless, that’s what made the term popular in the West. Of course, there is a whole martial-arts community that’s separate from that tradition and has a life of its own.
By the 19th century there were prints of dark-robed men stealing over castle walls.
Yes, there were some prints that were in operation. The myths that had been assiduously cultivated really spread only after [the ninja heyday], as it became ever more removed from reality. When I started this book, I thought I was going to be involved in all sorts of nonsense which is currently believed about ninja. But I was absolutely delighted to realize there was a historical core to them. And that’s really what the book is about. And even though ninjitsu is considered a martial art, there is very little to do that in the way of authenticity.
Could you talk more about the nonsense?
You look up ninja websites and ninja books and there are titles about the art of invisibility or how to disappear, which has been invented largely since 1945 in order to create and sustain a ninja community, many of whom dispute among themselves what is meant by true ninja-ism and what is authentic. There are masters still in existence who claim to have scrolls that go back to the Middle Ages granting them all sorts of authenticity down the generations, but nobody has seen these scrolls or proved anything about them.