Set in the future, the story follows a young soldier named Johnny Rico and his exploits in the Mobile Infantry. Rico's military career progresses from recruit to non-commissioned officer and finally to officer against the backdrop of an interstellar war between mankind and an arachnoid species known as "the Bugs."

Juan "Johnny" Rico, a high school student living in Buenos Aires, joins the Federation military in the hope of following his love, Carmen, into space. He has to undergo harsh training to become a soldier, harsher than he expected, but despite several setbacks and traumatic experiences, Johnny perseveres and finishes his training. However, a war is brewing on the outer planets with a strange alien enemy and Johnny is thrust into the conflict.