The Void Insect Species emerging from the northern battlefield of the Spiderweb Domain is absolutely linked with the Iron Armor Battle Group.
Otherwise, how could the timing be so immaculate?
As soon as the northern line encounters the Insect Race, the Iron Armor can instantly deploy a massive offensive on the western line?
Considering the Iron Armor's rise began with resisting the Void Insect Species in the Princess Star Domain, for the past century they would ask the Empire for money, using this reason. Often, giving them the money would suppress the Void Insect Species; not giving would make the conditions in the Princess Star Domain and its surroundings quickly 'decay.' Once paid, Iron Armor can immediately stand up and drive the Void Insect Species back.
As if the Void Insect Species was something they raised.
Of course, that's impossible.
At least that's what people believed in the past.