Isn't it an exaggeration that the Darkness Empire are a global Empire. They are like the Aztec Empire shoved in an age where industrialization is in full swing and Xia is leading the pack, so just from being more thecnologically advance so Xia should immidiatly declare war against them so they cant modernize.
The Darkness Empire is young and it doesn't have a modern infrastructure because they were fighting natives.
Reguku