The CIB means the wearer served in ground combat as an
infantryman tasked to take out enemy grunts with exactly the same
agenda. It also means he probably: lived like an animal in an
underground hole or bunker for long periods while mortar and artillery
shells thumped down all around him; slogged through the horrors of
knee-high mud, which can reduce unopposed movement to a mile a
day and make digging a foxhole an exhausting, slo-mo exercise in
futility; and endured the blazing sun, the freezing cold, the ubiquitous
dust that clogs every pore, the miserable rains that soak and chill to
the bone and turn living on the ground into the ultimate nightmare.
And, of course, there's the unrelenting, ever-present
second-by-second promise of sudden, violent death.