Crossbow.

[asomotif]

Originally Posted by Jim MacDougald

...have spent a lot of time researching it, including buying all the books I can find....
.... I believe that both explanations from the "experts" are wrong. I believe that the steel bowstring was used because of the enormous strength required to bend this very thick steel bow. Normal bowstrings couldn't handle the task....
....Jim MacDougald

Welcome Jim.
Crossbows is out of my league, but did you check the book : "Crossbows in the Netherlands Army Museum".

Best regards,
Willem