The Secret of the Submarine

The Secret of the Submarine is a 1915 American adventure film serial directed by George L. Sargent. It was 15 chapters and all of them are considered to be lost.
Plot.
The heroes must keep the titular submarine from falling into the hands of the Russians or Japanese.
Production.
Secret of the submarine was written in the lead up to the United States' involvement in World War I by war correspondent Richard Barry. The serial was released 15 days after the Lusitania was torpedoed by a German sub.