‘a WW1 battle involving tanks (which I believe weren’t in existence then’
They were by the end of the war. The British Mk1 was the first tank to be mass produced and that came into service during WW1.
Correct. Read about them in the battle of Cambrai.
Checked and you are 100% correct!
But did the Germans have tanks in a battle with the Japanese?
This is probably a stupid question, but I would really like to be proved wrong and see Aidan proved right.