The war began in 2357 when the Helghan Empire, under the leadership of Scolar Visari, sought to dramatically expand itself by invading Vekta, then invading Earth once Vekta was conquered, and destroying the UCN. Any opposition from the ISA-controlled systems would be crushed in a subsequent invasion of all other Human colonies. However, the ISA and UCA forces repelled the Helghast from Vekta.
In 2359, the ISA launched a counter-invasion of Helghan in an attempt to end the conflict by capturing Scolar Visari. But the assault failed with the death of Visari and the ISA forces were routed and forced to retreat. In 2360, the Helghan Empire plotted to directly invade Earth and bombard the planet with irradiated petrusite warheads. However, the Helghan government, without Visari's leadership, fell into civil war over who was to be Visari's successor. Combined with the in-fighting, a small ISA remnant prevented the Helghast plot and inadvertently detonating a payload of petrusite over Helghan, utterly devastating the planet in what became known as the Terracide, which marked the end of the war.
The roots of the Second Extrasolar War trace back to the First Extrasolar War. The first war from over one hundred years ago resulted in the dismantlement of the Helghan Corporation and Vekta, once a planetary holding of the Helghan Corporation, was turned over to ISA control. Colonists from Earth were brought to Vekta to supplement the planet's corporate-affiliated population. The introduction of the colonists brought violent tensions between the Earth minority and Helghan corporate majority, and resulting in the Helghan corporate colonists relocating to the planet Helghan, where they declared their sovereignty.
The colonists endured Helghan's harsh environment, transforming the later generation into the current day Helghast, and was subjected to ISA blockades and restrictions until diplomatic relations were normalized. From 2330 to 2350, Helghan was hit hard by a major economic depression, leading to widespread poverty and famine across the planet. The dire situation gave rise to Scolar Visari, who staged a successful popular coup against the ruling Helghan Administration in 2347, and declared himself the "Autarch". Under Visari, he reforged Helghan into a militaristic and xenophobic society, and later renewing hostility with the ISA and UCN, and determining to reconquer Vekta and expanding his empire across the stars.
Invasion of VektaEdit
The first stage in the Helghast's expansionist plans was the reclamation of the ISA controlled world of Vekta beginning in August 2357. Initially the ISA suffered massive casualties and territorial losses on Vekta after the Orbital Defence Systems 'malfunctioned', opening up the planet to a mass invasion force, and with a pair of high ranking double agents, the Helghast managed to take large swaths of territory and inflict severe ISA casualties in a savage blitzkrieg. However, due to the actions of Jan Templar and UCN reinforcements, the invasion was eventually halted and pushed back, and the few remaining Helghast of the Third Army were forced to fall back and regroup.
Two months later, Scolar Visari appointed General Armin Metrac to take full command of the Third Army along with the Eighth and the Ninth Helghan Army in taking southern Vekta. Under Metrac's leadership, the Helghast were able to establish a stronghold in the the Adlez Mountains and relentlessly taking over the eastern continent. However, by January 2358, the Helghast were forced into retreat before making one last decisive battle in the Redavni Plains which cost Metrac's life at the hands of Jan Templar. All remaining Helghast forces left on Vekta fell under the leadership of the treacherous ISA General Dwight Stratson and continued their resistance until Stratson was also defeated by Templar and arrested by the ISA. Despite of the Helghast having failed to reclaim Vekta, they managed to stole nuclear weapons from the ISA and brought them to Helghan.
Invasion of HelghanEdit
Two years later, the Helghast homeworld of Helghan was invaded by the ISA in November 2359 in an attempt to capture Visari and establish an easy-to-control puppet state. However, the ISA invasion was to fail due to unexpected fierce resistance from the Helghast, culminating in the nuclear devastation of their own capital, killing the ISA soldiers attacking it, and in turn the bulk of the ground invasion force. Also, the destruction of many of their cruisers, including the flagship New Sun, and finally the death of their fleet commander Colonel Jan Templar, by a large counterattack led by Colonel Radec has handed dominion of space and air to the Helghast, who bombarded the remaining ISA forces and overwhelm the few remaining ISA cruisers.
Finally, Scolar Visari, the ambitious emperor of the Helghast and the objective for the entire campaign, was gunned down by ISA soldier Rico Velasquez before he could be taken into custody, causing the ISA to stage a frantic evacuation, which quickly devolved to a total rout, in a hurried and unsuccessful effort to withdraw from Helghan. Roughly six months after their defeat on Helghan, the Vektan government capitulated to the Empire, formally ending the war in a status quo ante bellum as neither side could counterattack after that time, although the Helghast government played it off as the Empire's victory. However, conflict persisted between the Empire and ISA remnants on Helghan.
Helghan's Civil WarEdit
In the wake of Visari's death, a political conflict over who will assume the role of Autarch was waged between Admiral Orlock of the Helghast Military and Jorhan Stahl, influential chairman of the private weapons manufacturer, Stahl Arms. As the remnants of the ISA fought to survive, Stahl developed weapons using irradiated petrusite gathered from the Pyrrhus nuclear blast zone, such as a new Arc Cannon or irradiated petrusite-based perimeter defenses and energy shielding. In particular, an experimental flagship built by Stahl carried hundreds of missiles whose warheads were filled with irradiated petrusite and, alongside a massive Helghast invasion fleet, planned to eradicate all life on Earth by saturating the entire planet with the new petrusite missiles.
However, the political struggle between now-Autarch Orlock and Jorhan Stahl began to escalate, with successful operations conducted by the ISA remnant only making the situation worse. Eventually, the political conflict came to a climax aboard a Helghast space station, resulting in the death of Autarch Orlock and the Helghast race being plunged into civil war. This allowed the remaining ISA forces to destroy Stahl's cruiser with hijacked Helghast strike fighters, causing it to plummet to, then explode in low orbit over Helghan. The cruiser's destructive payload of irradiated petrusite missiles then detonated due to secondary explosions, with the resulting wave of energized radiation incinerating the entire Helghast invasion fleet, a large space station, and violently irradiating all life on Helghan. Managing to avoid the cataclysmic explosion in time, the remaining ISA troops onboard the hijacked strike fighters then made their way back home to Vekta.
The Second Extrasolar War was now at an end. With the devastation of the Helghast species and complete destruction of their military, industry and leadership, the ISA have emerged as a pyrrhic victor, despite a near total loss of their military resources and personnel.
With the ISA down to possibly around 100,000 personnel from a peak of two million and possibly as little as 6 ISA cruisers out of the 288 cruisers in the ISA Fleet during the Invasion of Helghan. While secretly a few thousand Helghast soldiers hid in underground bunkers on Helghan.
The surviving Helghast and their remaining ships were given an escort to Vekta by the remaining cruisers in the ISA fleet. After having relocated to Vekta, some Helghast exacted small amounts of revenge on the humans living on their half of the planet before the government decided to evict all non-Helghast beings from their territory. The Helghast and human communities are then separated by a massive wall in Vekta City, tensions run high, putting the opposing factions in a cold war scenario and setting up the events of Killzone: Shadow Fall.