In the 23rd century, Earth is under the control of the United Citizen Federation, a Stratocratic regime established by military veterans after democracy and social scientists brought civilization to its knees. Within this system, citizenship is a privilege granted solely through military service, leading to essential rights such as procreation and voting, which are denied to non-citizens. This societal structure promotes the idea that performing one's duty to the Federation is a collective responsibility.
As Earth expands into a space-faring civilization, humans unleash their ambitions on new planets, only to inevitably clash with a menacing Insectoid race known as the Arachnids, or "Bugs," originating from the distant planet Klendathu. These creatures are perceived as ruthless, relentless killers, although it is suggested that their aggression may stem from humans encroaching upon their territory. In retaliation, the Bugs send meteors hurtling toward Earth, prompting massive defense operations involving enormous spaceships that blast the meteors into oblivion. The invasion of Klendathu has become paramount for Earth's survival, leading to plans for a large-scale assault in a year’s time.
John "Johnny" Rico (Casper Van Dien), along with his girlfriend Carmen Ibanez (Denise Richards) and best friend Carl Jenkins (played by Neil Patrick Harris), navigate their high school life in Buenos Aires. The often overlooked yet passionate Isabel "Dizzy" Flores (Dina Meyer) harbors feelings for Rico, an affection he does not return, as he remains enamored with Carmen. Their teacher, Jean Rasczak (who is notably one-armed), guides them through their formative years.
Each character aspires to attend Fleet Academy, where they undergo rigorous assessments. There, Carmen impresses with a stellar 97% on her math test, while Rico struggles with only 35%. His lack of telepathic skills contrasts sharply with Carl's proficiency as a psychic. Meanwhile, Carmen’s flirtations with the athletic Zander Barcalow add to the complexities of their friendships.
Rico's parents, concerned about their son's choice, pressure him to pursue traditional education at Harvard University instead, citing the perils of military life. Despite their affluence and promises of a luxurious trip to the galaxy's outer rings, Rico yearns for independence and to establish his own identity.
During a graduation party, Rasczak imparts wisdom, asserting that one's path in life is the only true freedom they possess. Ultimately, after graduation, the friends enlist in the Federal Service, with Carmen convincing Rico and Carl to pledge lifelong friendship. Yet, Rico's declaration of love for Carmen goes unreturned, reflecting their diverging paths.
Carmen takes on the role of a spaceship pilot aboard the battleship Rodger Young, while Carl shines in Military Intelligence. Expecting to share the same unit, Rico is shocked to find Dizzy has transferred into his squad, intent on being near him. Despite her affections, Rico keeps his distance.
Their training under Sgt. Zim (Clancy Brown) is intense, with Rico rising through the ranks following a blend of luck and Dizzy’s guidance during training simulations. However, a dogged Zander continues to flirt with Carmen, leading to tensions.
After a tragic live-fire exercise results in a teammate's death, Rico faces demotion and turmoil. When an asteroid hits Buenos Aires, claiming his family's lives, he resolves to remain with the Infantry, fueled by vengeance. This catastrophic event leads to Rico's reinvention as the infantry deploys to Klendathu, where the mission quickly unravels into chaos.
In the battle against the Arachnids, Rico sustains serious injuries and is mistakenly classified as KIA, creating heartbreak for Carmen, who believes he is dead. After recovering, he rejoines his unit, the Roughnecks, earning respect from his former teacher, Rasczak. A catastrophic encounter reveals a cunning Brain Bug directing the Arachnids, prompting a desperate mission to capture this formidable foe.
With friendship and sacrifice at its core, the narrative reaches a peak as Rico’s team faces countless trials, culminating in emotional losses and deep personal connections. The harrowing journey ultimately leads to Rico standing as a central figure, embodying courage and resilience, as Carmen and Zander are caught in fatal circumstances, prompting Rico to confront the Brain Bug in a gripping standoff. As Rico’s fate intertwines with the political machinations of military leadership, he emerges as a beacon of hope amidst the chaos, ultimately leading humanity towards possible victory and camaraderie.
The film culminates with a powerful propaganda message showcasing Rico, Carmen, and Ace as exemplary soldiers, encouraging enlistment as a nod to the enduring themes of sacrifice and duty.
