This is interesting: this link at the official website of the ultra-secret National Security Agency will take you to a section of their site that deals with Freedom of Information Act requests.
As you'll also note, the NSA has titled the section: "UFO Related Information (No Records Exist)."
Notably, it's all listed alphabetically; and if you scroll down to the "U" section you'll see that someone requested information from the NSA on Japan's notorious Unit 731 - whose work formed the crux of my Body Snatchers in the Desert book.
How intriguing that the NSA should list the Unit 731 FOIA request in the "UFO Related Information" section.
Did the requester ask for any documentation that specifically linked Unit 731 with Roswell? And if so, was that the reason why the Unit 731 data was listed on that particular UFO-related web-page by the NSA?
Or, does the NSA have its own reasons, and knowledge, for linking UFOs and Unit 731 under one banner...?