In addition to what Mr. Harsey has so graciously posted, not only the dagger, but a lot of the combatives used can be traced back to Shanghai and the same time frame, as well as point shooting (although Col. Applegate greatly refined the point shooting).
The foundations of the combatives are in street jujitsu, modified for Anglos by Fairbairn et al and modified further for use with military gear by the Marines, Col. Applegate and others.
My combatives mentor maintains his ties with formal jujitsu as well as the combatives lineage. A lot of the old books show techniques very much like what the Gracies for example teach.
That the combatives are still viable even today says much for the skill of these men. We owe them a debt of gratitude.
Here's a good article by Dennis Martin on what Mr. Harsey is talking about.
The Source
Great story Mr. Harsey, thanks for sharing.