George Barton - The World's Greatest Military Spies and Secret Service Agents (1917)
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An assorted collection of light-reading stories covering King Philip's War, the American Civil War, the Napoleonic wars and others. Barton wrote a similar book about the first world war and then several fictional stories about a retired spy named Bromley Barnes that appear to be little read even by fans of the genre. (About the only non-bibliographic reference I can find called the stories "obvious".)