Teenagers with rifles who are acting as armed combatants are definitely not children.

Ten year olds who act as scouts for Hamas fighters are also combatants, not children.

The whole concept of childhood extending to age 18 is an entirely Western concept which has no place in Islam or indeed many non-Western cultures.

[Mohammed married Aisha when she was 6 years old and consumated at 9 years old.]
(https://sunnah.com/bukhari/67/70)