Ronald Duncan

June 15, 2026

Ronald Duncan was a real martial artist and an important Black pioneer in an American scene that routinely shut Black instructors out. He performed publicly, taught for decades and built a following. None of that makes his Koga Ryū ninjutsu authority real. That is the fraud in this file.

Ronald Duncan: The claim

Duncan’s name was used with Koga Ryū Ninjutsu, not merely as a loose description of self-defence. A book-page endorsement identifies him as “10th Dan Shinobi Koga Ninjutsu”; another calls him “Headmaster of Koga Ryu Ninjutsu”.[2][3] A later family and student tribute says he was teaching Koga Ryū by 1959 and presents the Way of the Winds system as the product of a broad collection of boxing, judo, jujutsu, kempō and weapons training.[1]

That distinction matters. A man may create a useful modern system from the arts he has studied. He may teach it honestly as his own system. But Koga Ryū is not a fashionable label for “martial arts with stealth and weapons”. It is a claim to a particular Japanese historical inheritance. Once that label is used to support high rank, headmastership or ninja authority, the evidence must show the transmission.

What is real

It would be lazy to turn Duncan into a cartoon. Contemporary and later coverage places him at major martial-arts events, records his public demonstrations and credits him with helping popularise ninjutsu in the United States.[4][7] The surviving biography also identifies named training in boxing, kempō, judo, jujutsu and weapons work, including his association with Naraki Hara.[1] Those are substantive martial-arts credentials, not evidence of an inherited Koga lineage.

There is an awkward detail in the material preserved by his own circle. A quoted 1971 Official Karate profile says that Duncan did not call himself a master of ninjutsu. Later material placed the much grander labels “10th Dan Shinobi Koga Ninjutsu” and “Headmaster of Koga Ryu Ninjutsu” beside his name.[1][2][3] That is not a documented chain of succession. It is escalation of status.

The missing lineage

The promotional account gives names for much of Duncan’s modern martial education, but it does not identify a Koga Ryū teacher, a Japanese licence, a recognised succession or documentary provenance that could carry his Koga claim. It jumps from a varied American martial career to teaching Koga Ryū. That gap is the whole case.

Serious classical-martial-arts researchers draw a sharp line between modern ninjutsu systems and koryū bujutsu: their objection is not that modern training is automatically worthless, but that it does not demonstrate continuous transmission of a classical tradition.[5]

This is not an abstract standard. Seiko Fujita (1898–1966), the fourteenth and final head of the Kōga Ryū Wada-ha, stated that he had not taught and would not teach anyone his ninjutsu, and that the school would end with him. He appointed no heir.[6][8] His surviving collection was preserved as archive material: the Fujita Seiko Bunko of books, scrolls and historical documents went to Odawara, while related weapons, tools and attire were bequeathed to the Iga-ryū Ninja Museum.[6] It did not become a chain of private Koga successors.

That fact makes the problem with Duncan’s claim very plain. A Koga lineage cannot be supplied by costume, public demonstrations or an impressive list of other martial arts. It requires an identifiable route around Fujita’s explicit decision to end the Wada-ha transmission. No such route has been produced.

Ronald Duncan: The verdict

Duncan’s actual contribution was as a martial artist, demonstrator and creator of the Way of the Winds system. That would have been enough. Dressing a modern synthesis in the authority of Koga Ryū ninjutsu was not.

There is no independently verifiable transmission supporting the Koga claim, no named and documented route from a recognised Japanese source to Duncan, and no reason to treat the later grandmaster language as anything more than a marketing credential. The Koga Ryū identity was presented as inherited authority without the evidence that inherited authority requires. That is fraudulent in substance.

Sources

Sources:

Bullshit Martial Arts