When you have time, you might wish to track down the history of Krupp[1]. A German company, they sold arms to all sides in WWI, having gained the the freedom to do so by previously threatening the Kaiser with moving their operations to Russia.

My recollection is that Krupp was paid a premium based on the effectiveness of their artillery shells - which, again, were being sold to both sides. Said effectiveness was calculated based on casualty numbers... so the more soldiers died (on both sides) the more Krupp was paid.

1. https://en.wikipedia.org/wiki/Krupp