The Kaiju are major/secondary antagonists movie Pacific Rim. Their name drives from the Japanese movie monsters, from which they are homages to. Intially though by humans as natural giant monster from other world, but later revealed as organic superweapons of Precursors near the end of the Kaiju War.
Kaiju are races of mass-produced colossal bio-weapons that controlled by Precursors, race of aliens that see humans as rotents and used to attacked the populated areas of Earth to conquer it. They are created from a strands from one of Precursors' DNA, which explained their phenotype difference from one with another albeit their genotype are identical. During it's earlier creation, Precursors mass produced prototype version that greatly resembles Knifehead type, then modified their body via surgery so each kaiju has different forms and powers, like Otachi the winged kaiju with acid thrower, and Leatherback the EMP blaster kaiju.
Once created, precursors control it via drift, and pit it with other variant until strongest won. The strongest kaiju then sent to Earth via breach, portal which opened in pacific ocean and designed so only kaiju can pass through.
During the Triassic Period, the Precursors attempted to colonize the Earth, but the environment proved to be uninhabitable for them and prevented them from inhabiting the planet. They bided their time until Earth's environment was ready for the Precursor's colonization.[4
Creation of the Breach
The progressive pollution of the Earth's environment by mankind made it possible for the Precursors to survive on the planet and colonize it. In response, they created a race of amphibious creatures, biological superweapons later known as the Kaiju by the humans. Shortly thereafter, the Precursors create a portal that bridges their universe to Earth on floor of the Mariana Trench.
The Kaiju first appeared on August 10th, 2013 in San Francisco. The beginning of the incident was a 7.1 earthquake; however, a massive, three-hundred-foot creature, later known as "Trespasser," emerged from the San Francisco Bay and attacked the Golden Gate Bridge. After destroying the bridge, the creature proceeded towards San Francisco and caused major devastation and cut a three-mile-wide path of destruction through the city. The massive creature then went on a 35 mile assault across the West Coast that lasted for six days. It continued on to Sacramento and Oakland, causing massive destruction in its attack. The United States and British militaries responded to the attack and battled the creature for a long six days. With the use of troops, tanks, artillery and jets, the combined forces of the Americans and the British failed to kill the massive beast. On August 15th, the military decided on using tactical nuclear missiles in the hopes of bringing down the giant beast. The military succeeded in taking down the creature with three tactical nuclear missiles. With the end of the destruction, three cities were left devastated and tens of thousands of people had died. The dead were mourned, the event was memorialized and humanity moved on. The incident in San Francisco was later known as "K-DAY"
Trespasser's attacks on the three Californian cities was thought to be an isolated event. But then, six months later, Hundun appeared and attacked the Filipino capital of Manila. Four months after that, Kaiceph made landfall at Cabo San Lucas and devastated it. As Kaiju began to appear in increasing frequency, nothing short of nuclear options proved capable of stopping them.
Scissure then attackedSydney on September 2nd, 2014. As Scissure neared the city, the Australian military lured it away and deployed a nuclear missile against it. The attack failed, and the creature proceeded towards the city and began laying waste to it. After three days, the military again lured the creature away from the city, hoping to deploy another nuclear missile against it while sparing the city the effects of the nuclear fallout. The nuclear missile was deployed, but though it killed the beast, half the city was destroyed by the blast.
It was clear that continued use of nuclear weapons was pyrrhic; the environmental devastation was far too great a cost. Therefore, after the Sydney attack, Dr. Jasper Schoenfeld began to contemplate how to protect the populace without resorting to nuclear weapons. Inspired by his son's robot and monster action figures, Schoenfeld and Caitlin Lightcap managed to create a prototype that would lead to full production of the Jaegers.
Numerous Kaiju attacked various cities along the Pacific Rim and were met with resistance by the Pan Pacific Defense Corps' Jaegers. Over the next five years, Kaiju slowly adapted to the Jaeger's strength. However, it was the belief of the Defense Corps that the invading creatures were losing to the combined efforts of humanity.
They remained unaware that Kaiju's specific reason for attacking large cities and populaces was to cleanse the environment of "vermin"; in this case, humankind. The information provided by the Jaeger battles allowed the Precursors to create Kaiju with specific abilities or strengths in a series of "waves". In accordance to their increasing size and strength, the Defense Corps created a "Category" scale, classifying Kaiju on the basis of toxicity and water displacement.
By 2020, Category III and IV Kaiju were becoming common Kaiju to attack the Pacific. February 2020 marked the beginning of the Defense Corps' downfall in the war against the Kaiju when the Category III Kaiju, Knifehead exhibits the learning curve that allowed it to partially destroy the Mark-3 Jaeger, Gipsy Danger and kill one of its pilots.
As the Kaiju begin to best the Jaegers, the United Nations put into motion plans to create a Wall that would isolate the Pacific Rim from the rest of the world in the hope that it would stop the Kaiju from spreading and began to move civilians further inland from the coastlines.
By the end of 2024, there were forty six confirmed Kaiju attacks. Fourteen were in 2024 alone resulting in staggering Jaeger losses. Hermann Gottlieb speculated in the aftermath of the assault on Sydney by Mutavorethat the increasing appearance of the Kaiju and their attacks suggested that the emergence of Kaiju from the portal would increase until there were mere day or hour lulls in their attacks, leading to the "Double Event" and "Triple Event".
Gottlieb's fears were later confirmed when his colleague, Newton Geiszler, "drifted" with a Kaiju's brain in order to gain information from the secondary brain in the K-Science Lab. Newton learned the first wave of Kaiju sent through the portal were meant to both test and weaken the boundaries of inhabitants defenses. The second wave of Kaiju would have adapted to the battle strategies of humankind and proceed to wipe them out in a mass extinction event.
Leatherback and Otachi simultaneously attacked Hong Kong in search for Newton, and during the process destroyed two of the four remaining Jaegers, Cherno Alpha and Crimson Typhoon. The Triple Event later occurred during the mission to bomb the portal. Scunner, Raiju and Slattern all emerged from the portal to defend their masters from certain destruction at the hands of Striker Eureka and Gipsy Danger. The Kaiju and their masters, within the boundaries of the portal, were destroyed when Gipsy Danger's nuclear reactor was set to self-destruct. The destruction of the breach ended the Kaiju War and destroyed the facility of Kaiju clones.