Hidden in a col surrounded by dense trees more than forty kilometers to the east of Dragon City was a wolframite mine. Among all the mines Dragon Citizens had discovered, it had the highest number of ores, and they were of the highest quality.
Wolframite alloy was an important raw material necessary to create armor-piercing shells.
And in an environment where sophisticated electronic equipment suffered from high failure rate and there were no satellite networks beyond the ozone layer to provide navigation, armor-piercing shells became the most important spear of humanity's steel army. It could even be said to be their only spear.
In the past, due to a lack of large quantities of wolframite ore, the humans were not able to produce a lot of armor-piercing shells.