This is an excerpt from a letter written by a soldier fighting in World War I and sent to his mother:
The trenches stretch for miles, but even though they are
almost 12 feet deep, we can't walk around much. The
bullets and grenades rain down upon us at even the
slightest hint of movement, so all we can do is lean in
stillness, waiting, trying not to make a sound.
Which statement best represents the main idea of this source?