> In 1814, for example, Napoleon conscripted many teenagers for his armies.[28] Thousands of children participated on all sides of the First World War and the Second World War.[29][30][31][32] Children continued to be used throughout the 20th and early 21st century on every continent, with concentrations in parts of Africa, Latin America, and the Middle East.[33] Only since the turn of the millennium have international efforts begun to limit and reduce the military use of children.

https://en.m.wikipedia.org/wiki/Children_in_the_military

I can see how it would be controversial because an argument could be made that children only are useful when you have some kind of artillery that doesn’t require the strength needed for a bow / crossbow. Still, I wouldn’t discount anything, especially on the purely modern subjective view of “it wouldn’t make financial sense”. Lots of human endeavors and actions don’t make financial sense. It’s not the only axis upon which humans behave.

I suspect of the controversy probably arises from the age “child” denotes. Is it a prepubescent human (lets say 10 and under) or a teenager (let’s say 13 and over).