Note: According to Al Hubin's excellent Crime Fiction IV, this is an adventure of Jo Salis. However, in the Google-digitized pdf copy I have of this book, while it details many activities of spies, especially the actions of the narrator, the name 'Jo Salis' is never mentioned and the narrator is called 'Greener, the name of the author, on three occasions.
This book deals with the activities of spies and war correspondents, and how they were largely indistinguishable, during the Port Arthur siege in the time of the Russo-Japanese War.