- "The time for diplomacy has passed, the Helghast do not see reason, they started this war when they invaded Vekta, and it's up to us to conclude it."
- —ISA spokesman, to UCBN News[src]
Operation Archangel was ISA Alpha Centauri's counterattack against the Helghast in retaliation for their invasion of Vekta during the Second Extrasolar War. The objective was to quickly end the war by capturing Autarch Scolar Visari and replacing the Helghast regime with an easily controlled government. However, the ISA were underestimated by the tenacity of the Helghast and failed to accomplish their goals, costing nearly the entire loss of their invasion force in the nuclear destruction of Pyrrhus, and Visari was killed and in turn prompting the Helghan First Army to destroy what is left of the ISA invasion force.
The ISA intended to defeat the Helghan Empire by arresting Autarch Scolar Visari and wrestling away control of Helghan, before establishing an easily controlled ISA-puppet regime to govern the planet, thus stopping the hatred and militarism that was the hallmark of Scolar Visari's reign. The plan was first put forward by the United Colonial Nations, in cooperation with the Vektan Council, to end the war and destroy the Helghan Empire. However, the UCN soon turned against the plan, preferring to isolate Helghan instead and keep Visari's forces bottled up with a significant force of blockading ships in orbit.
The Vektans; however, were utterly unwilling to see the Helghast go unpunished for the atrocities they committed on their world, and claimed that so long as Helghan remained unpacified, the whole of humanity would be threatened. The operation consisted of three waves of assault with a total of 12 ISA battle groups. The first wave was to secure a local firebase and capture the Helghast capital of Pyrrhus.
The second wave in which Battle Group Mandrake took part, had its primary objectives to capture Scolar Visari and eliminate the ground opposition as well as the remaining ships and orbital defenses. The third and final wave was in charge of deploying supporting troops to assist the ISA ground forces, aid the others battle groups and escort Battle Group Mandrake in their return to Vekta with Visari as prisoner of war to be judged for his war crimes. By 2359 the ISA put the plan into effect, acting against the mandate of the UCN whom continue to aid ISA efforts.
Under the command of now Colonel Jan Templar, the invasion soon failed as the ISA forces sorely underestimated the sheer scale of the Helghan defenses and resolve, as well as failing to take into account the charismatic leadership of Scolar Visari and the fanatical Colonel Mael Radec.
The ISA completely failed in their goals to capture Visari and nullifying any chance of ending the war. The ISA invasion force were severely weakened by the detonation of a stolen nuclear weapon in Pyrrhus which killed thousands of their troops, and later devastated by the subsequent Helghast counter-attack that destroyed the remainder of the ISA fleet and caused the ISA still on Helghan to become stranded. Scolar Visari was executed by Sergeant Rico Velasquez out of anger. The Helghast became now more hellbent than ever on destroying the ISA and UCN for the death of their leader and the devastation of their capital.