Was wondering if anyone can tell me of the first known instance of a tank running over a soldier? Most of the machines used in WWI weren't very fast and nimble.
I'd say that depends upon how nearly dead the unfortunate soldier was. If you're in a crater, with half your guts hanging out, I shouldn't think it matters how slowly a tank's going.
There is a passage in Frank Mitchell's book, Tank warfare, where he describes having to order his driver to drive along a section of road that is littered with the bodies of the dead and dying. His driver was reluctant but complied.
And I'm sure I've also read that there were some stubborn soldiers who refused to leave their machine gun and were squashed along with it, during the 100 days.