This is a transliteration of the Russian word диверсант, which means saboteur. From Cinepaternity: Fathers and Sons in Soviet and Post-Soviet Film by Helena Goscilo, Yana Hashamova:
The TV mini-series Diversant [The Saboteur, Andrei Maliukov 2004] depicts the rigorous training of young soldiers to transform them into professional saboteurs.1
I have never heard this word, it is not in the OED, and the GloWbE (corpus of web-based English) has only one instance of it, again referring to Germans.
My guess is that it is a German word which some writers have erroneously supposed existed in English.
Edit: Found it in German Wikipedia. It says it means a saboteur, in Communist-speak (and gives its origin from a Russian word Диверсия "Diversiya").