Uh... Humans from the 21st century!
Here is a very, VERY, VEEERY, important general from an AU in which we managed to create genetically crafted, sentient, four-legged, two-winged, fire-breathing Smaug-like dragons, who are able to communicate with us. We have technology similar to what your world had at the mid 20th century (around 1930s).
So. I managed to get myself into a PROBLEM. You know... My country is at war with a bordering nation. And obviously, ALL soldiers are dragon riders, thousands and thousands of them.
Luckily, we managed to capture one of their most well known dragons (the rider escaped our little trap. Worry not about him.), and chain it up on the wall. Well, the thing is BIG, like...Argentinosaurus big. We can't really kill it...since well, it has important information, AND we want to send a message to that country. They are losing so bad already that sparring this beast and letting it go back home would show how superior my country is to them, so NO KILLING IT.
But we have a little problem: How to torture it so bad that other country recognises their defeat?
Of course, we know that best way to attack those beasts is the back legs, tail, and wings. But I think that "back legs, wings, and tail" don't do very much for a weak spot. Therefore, my man won't be able gather useful information (or make it suffer enough to our purposes). Even if we opt to attack those areas, how do we pierce its bullet impenetrable scales or pick all the gems on its belly off so the soft plates get exposed, or even pull all his teeth off without getting toasted alive? Are those the best options for torturing this beast?