Robert W. Chambers

The Great War's secret side: a young American in the Intelligence service, a coded map, a Bolshevik agent, and a fortress in the Vosges. Chambers trained as an artist in Paris before turning to fiction, and The King in Yellow made him a name that Lovecraft would later borrow from; this 1919 thriller is the commercial Chambers, written fast and moving fast, with the war still in the room.