For longer than any of us have been alive, animals have traveled with military units in combat missions.
The most obvious mental image this fact tends to inspire is that of a medieval knight riding a horse into battle, but you're just as likely to see military dogs carry on important duties like finding explosives and neutralizing targets in modern times.
But even when the animals of war don't have official jobs, they tend to play important roles as they've been known to provide crucial comfort for veterans as they cope with the mental effects their missions have had on them.
Although we tend to picture emotional support animals as doing this once a soldier returns home, one heartwarming story of two veterans reuniting with their precious new friends shows this can happen in the field as well.