From a Washington Post editorial:

A prominent journalist of the World War II era complained once about the frequent use of the word “boys” when speaking of U.S. troops in the field. After what they’d been through, he said, they were not just a bunch of kids out on an adventure. In fact, the average age of those who died in the Second World War was about 27, and their numbers did include a good many youths. But the term was meant more as an expression of affection and solidarity — “our boys in uniform” — than as a description. It also reflected the poignant truth of their untimely deaths: much too young.