Prior to the modern era, the Royal Navy and others had boys sometimes 12 or younger on ships as servants, sometimes (those boys with higher ranks) being trained to be officers. The age for this sort of thing was gradually raised with time, but even during WW2 there were still minors serving on combat vessels. 134 boy seamen died when the HMS Royal Oak was sunk in 1939.

Yeah. I’m not sure where this certainty is coming from considering how youngsters couldn’t be part of the crusades considering they’ve historically always been involved in conflict:

> 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).

Yeah, I think the above comment is also underselling the strength of pre-teen children, or greatly overestimating the weight of arms, armor, and the strength needed to do things with horses. Children have worked on farms around horses ever since horses were domesticated. A sword or breastplate only weighs a few pounds, a knight could easily employ a pre-teen child to polish his armor, oil his sword, wax his boots, make his breakfast, or any number of other chores a knight doesn't want to bother with personally.

Swords and breastplate weigh far more than a "few pounds." Breastplate is close to 20lbs, a two-handed sword up to 10lbs. And that's just a small amount of the armor a knight would have (ignoring the fact that most warriors of the era wore chainmail, not plate).

Multiple children could work together to carry the armor. Pack animals would be responsible for carrying over longer distances.

The child obviously wouldn't be working as a pack mule. But is a 10 year old boy capable of lifting and polishing a 20lb breastplate? Certainly.

As far as I know, the draft in the US has always had a minimum age of 18, and one could volunteer at 17, but only with a parent's consent. Most young men grow considerably between 13 and 17.

Why is that relevant? There are also child soldiers even younger than 13, today. Just not in the US. Additionally, before the 21c US surveillance state, it was very easy to lie about your age in a way that would take a long time to verify. An enormous number of underage boys lied their way into WWII. If you were born at home, you may not have even had a birth certificate.

In the 19th century the US Navy used boy seamen as young as 14. In 1909 the regulations were changed to be 17 with parental permission, 18 without.

https://en.wikipedia.org/wiki/Boy_seaman

As late as WWII boys would routinely lie about their age to enlist early.