Sarah Kerrigan, former Terran Ghost and later the Queen of Blades, leader of the Zerg, was a major character in both the Starcraft I and Starcraft II video game series and has appeared in several novels that followed: Liberty's Crusade, Queen of Blades, Shadow of the Xel'naga, and Shadow Hunters.
Why was she abandoned on Antiga Prime by Arcturus Mengsk and left to be infested by the Zerg?
Having just replayed StarCraft 1 up to this betrayal, it was very apparent why Mengsk did it.
In the 3 missions preceding the betrayal Kerrigan she was told to use the psi-emitters to lure the zerg to a smaller confederate outpost. She did it but under heavy protest.
Kerrigan - I'm having doubts about this, Arcturus. I just don't think anyone deserves to have the Zerg unleashed on them.
Mengsk - I know you have personal feelings about this, but you can't let your past cloud your judgement. Carry out your orders, lieutenant.
later at the end of the mission.
Kerrigan - Psi-Emitter in place. Just promise me we'll never do anything like this again.
Mengsk - We will do whatever it takes to save humanity. Our responsibility is too great to do any less.
In the very next mission we make a breach in Tarsonis' defences, presumibly to send a strike force down to the planet. instead after the Breach Mengsk again deploys psi-emitters, and lures billions of zerg to the planet. This causes a major rift between with Kerrigan/Raynor on one side, and Mengsk on the other.
DUKE
This is Duke. The emitters are secured and on-line.
KERRIGAN
Who authorized the use of Psi-Emitters?
MENGSK
I did, lieutenant.
KERRIGAN
What? The Confederates on Antiga were bad enough, but now you're going to use the Zerg against an entire planet? This is insane.
RAYNOR
She's right, man. Think this through.
MENGSK
I have thought it through. Believe me. You all have your orders. Carry them out.
Following Kerrigans damming of Mengsk he sends her on 1 more mission, a mission to stop the Protoss who are unknowingly defending the remaining confederates on Tarsonis.
Mengsk :
If they engage the Zerg, the Confederates may escape.
Commander, send Lieutenant Kerrigan with a strike force to
engage the Protoss. Captain Raynor and General Duke will stay behind with the command ship.Raynor :
First you sell out every person on this world to the Zerg, then you ask us to go up against the Protoss? And you're goin' to send Kerrigan down there with no backup?
Mengsk :
I have absolute confidence in Kerrigan's ability to hold off the Protoss.
Raynor :
This is bullshit. Kerrigan, are you reading this?
Kerrigan :
I heard. I'm going down there. Arcturus knows what he's doing. I can't back out on him now.
Raynor :
Funny. I never thought of you as anyone's martyr.
RAYNOR
Why are you doing this, Kerrigan? Look. I know about your past. I mean, I've heard the rumors. I know you were a part of those
experiments with the Zerg; that Mengsk came and saved you, but you don't owe him this! Hell, I've saved you butt plenty of times.KERRIGAN
Jimmy, drop the knight-in-shining-armor routine. It suits you sometimes. Just not ... not now. I don't need to be rescued. I know what I'm doing. The Protoss are coming to destroy the entire planet, not just the Zerg. I know that because ... well I just know it. I am a Ghost, remember? Once we've dealt with the Protoss, we can do something about the Zerg. Arcturus will come around. I know he will.
RAYNOR
I hope you're right, darlin'. Good huntin'!
This mission is clearly a set up for Kerrigan, with Raynor stating, your going to send her in by herself, with no support, and Mengsk replying, dont worry she'll be fine. Obviously at the conclusion of this mission Mengsk again pulls a fast one and states, uh, cant get to her sorry Jim.
KERRIGAN
This is Kerrigan. We've neutralized the Protoss, but there's a wave of Zerg advancing on this position. We need immediate evac.
MENGSK
Belay that order. We're moving out.
RAYNOR
What? You're not just gonna leave them?
MENGSK
All ships prepare to move away from Tarsonis on my mark.
KERRIGAN
Uh, boys? How about that evac?
RAYNOR
Damn you, Arcturus! Don't do this.
MENGSK
It's done. Helmsman, signal the fleet, and take us out of orbit. Now!
KERRIGAN
Commander? Jim? What the hell's going on up there-
So with the books and extra material aside, they make it clear in game that Mengsk betrays Kerrigan because she is quickly becoming a tool he can no longer use, with her arguments and opposition to his plans.
Sarah Kerrigan, during her time as a Confederate Ghost, assassinated Mengsk's parents and sister.
When Korhal declared itself independent from the Confederacy, taking out the Mengsk family was one of their first actions, before they carpet-nuked the place as well. Kerrigan led the team.
While Arcturus later retrieved her from an experimental facility (some of the initial tests confirming the link between Zerg and psionics like Ghosts were done on Kerrigan), she had only fragmentary memories of her time as an assassin at best. She didn't recognize Arcturus or his name. He did. He befriended her and invited her to join the Sons of Korhal. Over time some of her memory returned, and Mengsk used her to take out the other Ghosts who had performed the kills, but supposedly forgave her once the others were dead.
He was content to use her as a highly effective tool against the Confederacy that once employed her against him. Once his victory over the Confederate capital Tarsonis was assured by psi-summoned Zerg, however, he coldly took his revenge by positioning her to assure the Zerg's success and then abandoning her. That it saved some of his forces the effort of killing Zerg that were killing Confederates probably didn't hurt.
The Mengsk's assassination is covered in the tie-in novel I, Mengsk along with some of Arcturus' family history. The start of Kerrigan and Mengsk's working relationship is shown in Starcraft: Uprising.
