The story begins with the childhood trauma of two young brothers, aged five and six, witnessing their Marine father's deployment, a moment that profoundly shapes their future. Their father is later killed during this deployment, leaving the boys orphaned and with a deep-seated desire to follow in his footsteps, intertwined with unresolved grief and anger. In their high school years, this inner turmoil manifests as frequent fights and a volatile temper. Their path takes a decisive turn when a Marine recruiter visits their school, planting the seed of enlistment with the proclamation, "The Marines make men." The younger brother is inspired and enlists after graduation. The older brother, initially pursuing college, ultimately abandons it to join his younger sibling, driven by a fierce protective instinct.

Their Marine journey leads them to the 1st Battalion, 6th Marine Regiment, affectionately known as "1/6 Hard," and into the heart of World War I. The narrative escalates to the brutal and legendary Battle of Belleau Wood in June 1918. The brothers encounter the terrifying realities of trench warfare and close-quarters combat, a realm far from the idealistic ideas of recruitment. During the fierce fighting, where Marines earned the moniker "Devil Dogs" for their tenacious ferocity against German forces, the older brother is tragically killed by a German soldier. His death, amidst the relentless carnage and the struggle to hold ground, solidifies the legacy of sacrifice and courage associated with the 1/6th and embodies the spirit of the Marines who fought and died at Belleau Wood.