One of the comments reads : Actually, we will probably never figure out, was it man or woman. but I thought this comment of the professor was an interesting eye opener. https://mastodonapp.uk/@MarkHoltom/112070436760917344
Seriously, the Fire Nation had mass produced internal combustion engines in ATLA. They put them in their mass produced tanks. Not to mention the fleet of ships with smokestacks indicating they probably had either diesel or steam powered ships. The Earth Kingdom and Water Tribes are both still in the process of industrializing, but the Fire Nation was already pretty much there, and the United Republic is primarily a Fire Nation breakaway state.