Molten Eagle: Deltiology Connection the Mainstream Missed

No, deltiology has little to do with riverine warfare. It is the study and collecting of postcards.
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Only the United states Post Office was allowed to print postcards until May 19, 1898, when Congress passed the Private Mailing Card Act allowing private printing. In the U.K. private printing had been authorized 4 years earlier.
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History (at least some of it) is recorded in postcards. Yes, even submarine history from the author's amateur postcard collection has appeared occasionally at Molten Eagle.
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A CONTROVERSIAL CONNECTION
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Picture postcards enabled people to send images across national borders, and the legal availability of a postcard image in one country did not guarantee that the card would not be inflammatory in the destination country, or those intermediate countries a card might pass through enroute.

In response to this new phenomenon, the Ottoman Empire banned the sale or importation of some materials relating to the Islamic prophet Muhammad in 1900. Affected postcards that were successfully sent through the OE before this date (and are postmarked accordingly) have a high rarity value and are considered valuable by collectors.
An example of a 1900 Muhammad postcard with high rarity value may be available on the internet, so if you find a link please let the rest of us know. Meanwhile, here's a 1920-30s Algerian example of Mohammed's Flight from Mecca in 622 AD. Mohammed is the figure in red about to enter a cave. The original postcard is in a private collection, not M.E.'s unfortunately.