Really? Is "putting your life on the line" the criteria you'd use? Gotta include cab drivers and fishermen then, because their jobs are many times more dangerous than either cops or firemen.
Saw you liked Ender’s Game, another great book. But yes, I do think the thinking of Heinlen in Starship Troopers is spot on. Will we ever get there?, Who knows. Dont know if you read the book; if not check it out, you’d probably like it.