In the 23rd century, Earth is run by military organizations. In order to be a proper "citizen"
and gain access to basic rights like voting and having a family, people must join the army. Around
this time humans also achieve space travel, and eventually they discover an insectoid species
of alien they call "bugs" from the planet of Klendathu. Since then, humans and bugs
have been in a constant war for territories, and military organizations keep releasing video ads to
promote the opportunity to fight for humanity’s future. These videos often include showing the
soldiers in the middle of battle, going after the bugs with all their weaponry and skills, but when
bugs manage to strike the soldiers back, the footage is cut off. In a school class on earth,
professor Rasczak is teaching his students about World History and the importance of the military,
but student Rico is more interested in sending silly doodles to his girlfriend Carmen. When
Rasczak asks Rico a question, he manages to answer correctly, but Rasczak still scolds him for only
repeating the text instead of showing actual understanding of it. After class, Rico and Carmen
check the results of their math exams. Carmen’s scores are great since she’s been studying hard
to be accepted into the Fleet Academy, which she’s desperate to join. When Rico checks his scores, he
discovers that he's only got 35%, and his friend Carl teases Rico by making the score bigger on the
screen for everyone to see. Afterward, Carl asks how things are going with Carmen, reminding him
that a girl named Dizzy is in love with him, but Rico insists that he only wants Carmen. Afterward,
they go to another class where they are taught how to open up a bug alien and identify all its
organs. Rico goes through it without any issues, but Carmen ends up feeling sick. In the afternoon,
Rico tests his psychic ability with Carl, who is a great psychic. Carl has even managed to send
messages directly into his pet’s brain, making it do whatever he wants. He tries to train Rico as
well, but Rico simply doesn’t have the skill and fails at guessing Carl’s cards. On the other hand,
Rico's a very good American football player and tonight there’s a game. During the match,
Rico notices an opposing player named Zander is flirting with Carmen, so he plays extra
violently to make sure they win. The team captain scolds him for being distracted,
but Rico’s jealousy makes him extra determined and after stealing the ball from Zander,
he manages to win the game. Not wanting to lose Carmen to some other guy, Rico decides to join
the military for her. When he tells his parents about it, they’re very disappointed and try to buy
him over with an exciting vacation trip to space, leaving him undecided. Later at the school dance,
Rico goes looking for Carmen, only to find her talking to Zander. Feeling jealous, Rico takes
Carmen away for a dance and Rico tells her that he will join the military with her. The next day at
the registration office, Rico signs up for the Mobile Infantry, Carmen joins the pilot unit,
and Carl gets into the intelligence division. The man receiving their paperwork is missing most of
his limbs, but this doesn’t scare them off. Before they go their separate ways, the trio makes a vow
that they will always be friends. At home, Rico gets into an argument with his parents over his
choice for the future. In the end, his father cuts him off of his money and Rico leaves the
house carrying nothing but what he's currently wearing. Afterward, at the departure station,
Rico and Carmen say goodbye, promising that they will always write letters to each other.
Meanwhile the military’s ads get more and more violent, showing the public the damage the bugs
are doing to their brave soldiers. Later at the training camp, the newbies meet their instructor
Sergeant Zim. Wanting to test the capabilities of the recruits, Zim asks if anyone wants to try to
take him down. One recruit volunteers and tries his best to attack, but Zim easily overpowers
him and gets his arm broken. At that moment Dizzy arrives, saying she requested to get transferred
to Zim's unit to be with Rico. Zim tests her too, and while he overpowers Dizzy easily as well,
at least Carmen has a few more moves and is allowed to stay. Later during lunch,
Rico calls out a recruit named Ace for cutting the line. Ace is rather impressed by the way
Rico stands up to him, and they end up becoming friends. The rest of the day, the recruits are
put through an intense training course that tests all their skills. When it’s time to throw knives,
Ace complains about the activity, and Zim punishes him by throwing a knife at his hand. Later in
the showers, the recruits share their reasons why they join the service, but when it's Rico's turn,
he doesn't want to talk about it. Dizzy tells everyone that Rico joins the service because of
a woman, and the whole squad teases Rico for it. Afterward, Rico records a video to send to Carmen
while everyone teases him in the background. Moments later, Carmen happily watches the
message before going back to flight training with her fellow recruits. She gets to fly a shuttle
for the first time, and her skills are quick and smooth, impressing her instructors. Carmen lands
the shuttle in a huge spaceship they’ll take to bug planet, and there she discovers Zander,
who has become an assistant instructor. She gets to pilot the huge spaceship for the first time,
and it almost hits the station, but Carmen has quick reflexes and swiftly takes them away.
Meanwhile Rico is doing well too. Using their knowledge of American Football, Rico and Dizzy
manage to take the win for their team during the capture the flag exercise, showing great
shooting skills and perfect teamwork, putting down every soldier in their way. Seeing that
Rico has potential, Zim promotes him as a squad leader. In the evening, Rico receives a message
from Carmen and is devastated to hear Carmen say she wants to break up because she wants to pursue
a full career in flying. Rico is now very sad and emotionally unstable. The next day, Rico's squad
partakes in a fighting simulation where they will be using live ammunition. At first it goes well
and they quickly shoot down their enemy, but one of Rico’s teammates has a helmet problem and Rico
takes it off. In the process, one of the recruits accidentally shoots the teammate in the head and
kills him. Later the recruit immediately resigns out of guilt, and Rico is relieved of his squad
command duty, which is transferred to Ace. After the meeting, Rico is tied up outside and given
something to bite on while he’s given a painful whipping for everyone to see. Meanwhile at the
spaceship, the captain wants Carmen and Zander to officially team up and join the crew. The two are
happy to hang out discussing tactics, and when they’re about to kiss, they’re interrupted by a
sudden shift of gravitational pull. Upon scanning, they discover that an asteroid from the quarantine
zone is approaching them fast. Carmen takes over the controls and manages to use her skills to
evade the asteroid with masterful emergency evasions, although part of the ship's still
lost in the process. Back to the Infantry, Rico’s resigning from the service. Dizzy tries to talk
him out of it, but since Carmen broke up with him, he has no reason to stay. Then Rico calls
his parents to apologize and tell them that he'll come home, but their call is suddenly interrupted
by signal interference. The newscast takes over all the screens at the base showing a devastating
update: the asteroid that's sent by the bugs has hit their hometown and killed millions of people,
including Rico’s parents. Due to the incident, the federal council decides to completely eliminate
the bugs on Klendathu, and Rico decides to stay to avenge his family. The Commander-in-chief doesn't
want to allow him to return to service because he formally signed off just a few minutes ago,
but Zim rips Rico's resignation letter to pretend it never existed. Meanwhile an advertisement from
the Military Intelligence Division shows how to properly kill the bugs. According to Carl,
who's now one of the leading researchers, targeting the bug's nerve stem can finally kill
it for good. This ad includes the Fleet Battle Station Ticonderoga, where a live broadcast shows
the preparation of the mobile infantry to attack Klendathu. Rico and the others get interviewed and
they are all eager to kill the bugs. The infantry and the pilot units come together for the attack,
and Rico is surprised to find Carmen. They try to talk about their relationship, but Carmen insists
that she did what's best for them. At that moment Zander arrives and Rico immediately understands
what is going on between Carmen and him. Wanting to be mature, Rico tries to leave but suddenly
Zander talks badly about the mobile infantry. Furious, Rico jumps and Zander and starts a
vicious fight, but they barely get to exchange a few hits before they are stopped by their
friends. Afterward, Rico and his squad go to get a tattoo to signify their goal to wipe out the bugs.
Sometime later, they all head out to Klendathu in a fleet of shuttles. However even before landing
on the planet, the soldiers are already being attacked by a light plasma. As various shuttles
are hit and begin exploding around them, Carmen and Zander do their best to avoid the attacks,
but they're still hit. When the soldiers who survive the initial aerial attacks land on
the planet, they waste no time and set up their counterattack. Up close, they see that the light
plasmas are coming from the bigger bugs. They begin their assault by nuking these big bugs,
then they all charge and an all-out war between humans and bugs begins. However the bugs have much
bigger numbers and quickly surround them, killing people left and right. Seeing their comrades
brutally murdered by the bugs, the mobile infantry starts to retreat as the bugs follow them and keep
killing whoever is too slow. The reporter covering the raid gets caught and eaten as well, but
since the cameraman won’t stop recording, a few soldiers have to cut in and rescue him by shooting
the monster. Unfortunately another bug takes advantage of this and attacks them by surprise,
killing them all rather quickly. Rico gets angry and doesn't stop shooting until he kills the bug,
but before it dies, the bug manages to wound Rico in his leg and he passes out. The next morning,
the Sky Marshal resigns due to his negligence to collect proper intel before launching an attack.
The new Sky Marshal lays downs her new strategy for dealing with the bugs, saying they need to
understand them. A military scientist suggests that there must be a leadership caste of hive
minds in the bug's society. Meanwhile Carmen and the crew manage to survive the hit in space,
flying around with a spaceship that is barely hanging in there. Upon returning to the station,
they find the lists of casualties, and Carmen’s devastated to see Rico on it. However this is
misinformation, Rico actually survived and is now currently being treated in a
medical facility at the base. It turns out he was rescued by Rasczak, who has joined the military
too and became a lieutenant of a separate unit. Dizzy and Ace come to visit Rico and
tease him for being listed as dead, thinking it’s hilarious. When Rico finally recovers,
he and his friends join Rasczak's unit called "Roughnecks", who are tasked with cleaning out the
bugs on every planet around Klendathu. The next day, the Roughnecks proceed with their mission.
After bombing the bugs from the air in a quick attack that cleans the area, they start searching
for bug holes to nuke. There are still a few bugs around, but they’re quick to shoot them to death
since the soldiers outnumber them now. When they nuke a particularly big tunnel, a gigantic bug
called "tanker" emerges from the ground and shoots flames from its antenna, causing everyone to start
running away. Rico stays and gets on top of the bug, shooting a hole into its skin before dropping
a grenade on the wound. Then he jumps away as the grenade explodes, killing the giant bug.
Everyone cheers for Rico’s victory, and Rasczak promotes Rico as his corporal. In return, Rico
makes Dizzy his squad leader. Later that night, the Roughnecks have a celebration. Rico finally
accepts to dance with Dizzy and invites her to his room, where they begin getting frisky. Their fun
time is cut short when Rasczak alerts Rico about the distress call they just got, but at least the
lieutenant gives them twenty minutes to get ready, so the new couple finishes their activities first.
The next day, the unit heads out to Planet P where the distress call came from. There, the
sergeant is suddenly taken away by a flying bug, so Rasczak has to shoot him to end his suffering.
He then tells his unit to do the same for him if he ever gets captured. Due to this sudden loss,
Rico is promoted to sergeant and Rasczak orders him to lead the team. Upon reaching the base in P,
they found nothing but dead and mutilated bodies everywhere. There’s a hole in the middle of the
base, which the bugs used to invade. They also discover something horrifying: all corpses have
an empty hole in their heads, implying that a bug sucked the brain of soldiers. All of a sudden,
they hear a noise coming from a tool cabinet. When they open it, they find a terrified general,
who reveals that before sucking the brain of the soldiers, the bug controlled them to call the
headquarters, meaning that the distress call is a trap. At that moment, thousands of bugs
start attacking them. The Roughnecks face the bugs with their weapons and the base’s cannons,
killing the creatures that try to climb up their walls. Unfortunately a new type of flying bug
joins the fight, making it harder for humans to defend themselves. With his shooting skills,
Rico manages to take down one of them, but it falls right on top of the general, accidentally
killing him. In the middle of the fight, Rasczak orders Rico to call the headquarters for help,
and while Rico asks for extraction, more bugs keep coming. It’s only a matter of time before they get
overrun so once Rico notifies Rasczak that help is coming, the lieutenant orders the unit to regroup.
While the bugs finally reach the top of the walls and the soldiers use their last bullets, Carmen’s
airship arrives to pick them up. Suddenly a tanker emerges beneath them and rips out Rasczak's legs,
so Rico must fulfill his promise and mercifully kill Rasczak. Dizzy acts fast and manages to kill
the tanker by throwing a grenade into its mouth, but she is distracted and gets stabbed by another
bug in return. Furious, Rico and Ace take down the bug and help Dizzy get into the ship while
a new tanker arrives and burns down a wall. At that moment, the ship flies out of the planet,
but unfortunately Dizzy succumbs to her wounds and dies. In the cockpit, Rico approaches Zander
and Carmen and orders the bombardment of Planet P. Carmen’s shockingly happy that Rico's alive,
however Rico is in a bad mood because he has lost many soldiers. His request is also denied
because the Sky Marshal has different plans for P. Moments later, Rico and the others pay their
respect to Dizzy and release her casket in space. Shortly after, Carl, who's now a colonel, arrives
and reunites with his friends. He apologizes for sending the Roughnecks unit on P and explains that
they needed to be sure that there’s a brain bug on the planet, even if it cost dozens of lives. Now
they’ve got confirmed intel, they’ll be able to set a proper mission. Carl then promotes Rico as
the new lieutenant and leader of the Roughnecks. Afterward, they land back on planet P where Rico
meets the new members of Roughnecks. As Rico welcomes them, the bugs start shooting light
plasmas in space. At this moment, Carmen's ship is hit directly and torn in half, causing the captain
to order them to abandon the ship and evacuate. On their way to the rescue deck, the captain
trips and gets pinned by a door seal. Carmen tries to help her, but the captain orders her to save
herself. Carmen and Zander run away and manage to escape through a pod, but unfortunately the pod
catches on fire during entry and crashes into a mountain cave, where they get surrounded by bugs.
After Carmen alerts Rico of their location, she and Zander begin to fight off the enemy, but it
doesn't take long before the bugs incapacitate the two of them. Hearing their scream on the radio,
Rico thinks that they're already dead and orders his unit to continue their mission to find the
brain bug through the cave tunnels. Meanwhile it’s revealed that the bugs have not killed
Carmen and Zander yet, they’re stabbed but also being kept as prisoners for the brain bug. While
the unit's going down the cave, Rico suddenly gets a gut feeling that Carmen's still alive, so
he orders his unit to continue the mission while Ace and Sugar go with him in searching for Carmen.
Back to Carmen and Zander, they’re terrified of the giant brain bug that finally shows itself.
Zander hands a knife to Carmen right before the nasty bug uses its fang to suck Zander's brain.
When it's Carmen's turn, she uses the knife to cut off the brain bug's fang. A bug is about to punish
Carmen for it, but it's stopped by the brain bug because Rico, Ace, and Sugar are arriving with a
nuke in hand. As Carmen slowly goes to Rico, the brain bug also backs away, and Ace alerts the team
that the bug is going in their direction. Once the brain bug's gone, the other bugs start attacking,
wounding Sugar in the struggle. He then sacrifices himself by triggering the nuke so Rico, Carmen,
and Ace can escape. The explosion kills all the bugs but also seals the tunnel. When the trio
finally gets out of the cave, they see all the soldiers celebrating. It’s then revealed that
the brain bug has been captured by Zim and is being dragged out in a net. Carl approaches
and reads its mind, revealing that the brain bug is afraid. As everyone cheers in victory,
Rico asks Carl if he's the one that telepathically told him that Carmen was alive, to which Carl says
it's classified. After the battle, Carmen is promoted to fleet captain, and Rico and Ace
become famous soldiers. The military uses them and the captured bug to advertise their organizations
and invite more people to join the mobile infantry, ready for the upcoming challenges.