The Interplanetary Strategic Alliance or ISA for short is the main military force of the United Colonial Nations (UCN) and is the main protagonist of the Killzone franchise. The ISA is meant to protect human colonies and the UCN and enfore the UCN's will if ordered to.    


Inauguration of the ISA

As human colonies expanded into many planets and star systems, the UCN began to notice a large gap of communication between both the UCN on earth and the Human Colonies in other systems. In response the ISA was created as a local military force for each colony but would unite to defend multiple colonies as a much larger military force. The UCN would provide training, equipment, and political support while the local cononial governments with funding and manpower. The ISA was to be both military and police forces for the human colonies and each local colonial government and authority would ultimatly report to UCN central command back on earth. In 2133 Alpha Centauri and Altair Systems became the first ISA command centers.

First Extrasolar War

During the colonization of Alpha Centauri, six colonial ships go missing leading to a massive finanical crisis for the UCN. the Helghan Corporation (HelgCorp.) soon colonized Helghan and the ISA colonized Vekta but the Helghan Corporation had massive amounts of money and refused to give some to the UCN and wanted to gain finaincial independnece due to laws and regulations the UCN had on space travel and trade. In response to the Helghan Corp's seccession threat, the ISA was sent in to prevent the Helghan Corp from leaving starting the First Extrasolar War in 2199. 5 years later in 2204 the war ended with a tactical ISA/UCN victory.

Blockade around Helghan and Rise of the Helgasts

After the Helghan Corporation was defeated, all human colonists with affiliation of the corporation fled to helghan. Helghan was a harsh desert world and the colonists were cut off due to the UCN forcing the ISA to block Helghan and cut off their supplies. the helghan Administration governed the planet but was corrupt and inefficient thus leading to the rise of Scolar Visari in 2347 and the creation of the Helghan Empire. The Helghast population began to become increasingly militaristic and under the leadership of Scolar Visari, the ISA was ordered to pull out due to the rising military dictatorship. 10 years kater in 2357 the Helghast Army launched a massive fullscale invasion of Vekta starting the Second Extrasolar War.

Second Extrasolar War

Helghast Invasion of Vekta

Following the rise of Scolar Visari as Autarch, the Helgast military had disabled the orbital defenses leaving the planet defensless in space. As helghast troops decended from above and landed and began their attack on Vekta, the ISA was soon deployed to prevent the planet from being taken over. The ISA forces were being oushed back at first as helghast forces had overwhelming numbers and most of the planet had already fallen. Despite odds against them however, the ISA had retaken the planet and the Helghasts were pushed back but a Red Dust nuclear bomb was stolen by them. Around 2360 about 3 years into the conflict the ISA were soon preparing to invade Helghan, home of the Helghasts.

Operation Archangel

In the year 2360 the ISA were already prepared and set to invade and attack Helghan in an effort to bring down the Helghan Empire and capture Helghast dictator, Scolar Visari. Visar had already known of the threat that he faced and made a live broadcast saying how he will repeal the invasion fleet and sent the ISA fleeing in flaming retreat. The primary goals were simle

  • Remove the Helghasts as a military threat
  • Capture Scolar Visari and hold him for a public trial
  • Establish an easily controled, Pro-UCN regime and stop the oppression that started the conflict.

Once the ISA ships arrived at Helghan, ISA cruisers were soon under fire from ARC Pillars and orbital defenses but managed to make it through to the surface where cruisers began to open fire on city defenses allowing the ISA Marines to fly onto the shores via Intruder troop transporters. The transporters were soon being shot down as ISA troops were landing and crashing onto the shores to be met by intense heavy resistance from Helghast soldiers on top of bridges, freeways, highways and slums and barely made it through.

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ISA soldier during Operation Archangel

Soon the Helghasts detonated red Sun and destroyed Pyrrhus city killing millions. Despite heavy bloodshed and massive casualties, Alpha Squad, a small team of ISA troopers had finally managed to make it to Visari's palace where the infmaous Colonel Radec, commander of the Helghast Forces defending Helghan, had attempted to defend Visari but failed and soon Sergent Tomas Sevchenko and Rico Velasquez found Visari where Rico shot Visari to death after Visari gave a speach claiming that the ISA had lost and the Helghasts were to be the true victors and then claimed that madness had begun as his last words. Sev soon sat on the palace stairs and witnessed in horror the oncoming onslaught of bloodthirsty Helghast soldiers.

Evacuation of Helghan

After Operation Archangel ended in disaster, the remaining ISA soldiers soon scrambled in desperation to escape the planet and were soom left scattered enough to be picked off one by one. Led by Jason Narville, Sev, Rico, and the remaining ISA soldiers had used what ever resources they could find and immediatly began to rush towards the Pyrrhus crater where ISA cruisers were to help escort them off the surface of the planet. As the ISA convoy began to head towards the city ruins for planetary evacuation, Helghast forces ambushed them and soon the convoy was scattered and Sev and Rico were soon forced to fight through the city ruins and eventually made up with a group of ISA soldiers regrouping around a ruined highway. After a bloody firefight, the convoy finally made it through and soon Avenger Convoy began to advance further destroying any Helghast resistance that met them however soon the ISA Forces encountered the MAWLRs, a massive Helghast battle walker that had enough firepower to bring down an entire cruiser and soon the ISA forces fled the city but Rico and many others were left behind.

Rescue from Stahl Arms and Invasion of Earth

6 months after the invasion of Helghan, the ISA Forces dispite bein in dissaray, were left untouched by the Helghasts. Somewhere on a lush rainforest world, ISA troops were waiting evacuation from Earth fleet when Helghast military forces caught up to them. Sev soon discovered a massve military buildup and soon petricide weapons were being used against ISA troops particually Bandit Recon which soon dsbanded upon the death of everysingle member. Sev soon fled back to the ISA Base Camp where it was being besieged by Helghast forces as the ISA troops fought hard and well but in  the end they were overwhelmed and Sev and Narville were captured as everyone else was killed. Rico then rescued Sev while being sent to an arctic facility for Stahl arms and with support from the raiders, all POWs including Narville were rescued and soon attempted to stop the Helghast invasion of earth. Chairman Stahl and his fleet now under the command of newly crowned Autarch Orlock began to amass an invasion fleet for earth when the ISA troops began to intercept the fleet and made it to the command space station and soon the Helghast fleet was soon being torn apart as Stahl's cruiser opened fire on ships loyal to the High Council forcing his cruiser to be attacked by ISA strikefighters and soon the cruiser crashed landed on helghan collapsong the Helghan Empire thus ending the second extrasolar war.

Military Structure

ISA Navy

Main naval force of the ISA. Mostly comprised of ISA Cruisers and other orbital defenses including Intruder Infantry Dropships, ISA VTOHLs, heavy VTOHL, space cruisers, and other space and universal military vehicles.

ISA Infantry

Main gorund force for the ISA. Mainly used for police and military purposes. During the invasion of Helghan they were deployed to the shores of Helghan but were met with relentless resistance and barely made it to the capitol.

ISA Marines

Ground forces for the Navy. usually deployed to support ground forces and defend cruisers if stationed on them. 5,000 out of a crew of 7,500 are marines onboard a cruiser.

Rapid Reaction Force

RRF for short, they are the first line of defense against any planetary invasion if orbital defenses fail. 

Special Forces

Main special forces (obviously) and are made up of two separate divisions. Shadow Marshels which are deployed on sabotage and assassination missions and the Covert Field Operations which are used for intelligence and information gathering.


the Vektan Security Agency, is the main intelligence division of the ISA and is stationed on Vekta. The main Headquarters is in the planet's capitol Vekta city and comes under attack by The Black Hand. The VSA first appears in Killzone: Shadowfall


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