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“Once Spartan Palmer secured the landing zone, a constant stream of UNSC forces was re-deployed to X50's surface. The Forerunner signal continued to loop, the scientists were having a hard time pinning down its exact origin point. Meanwhile, Covenant forces recaptured a series of turrets along a large gorge called the Arid Sea. UNSC would require significant fire power to break through. Spartan Palmer took command of a battalion of Scorpions and Grizzlies in an effort to eradicate the Covenant turrets. As she fought, UNSC scientists began to crack the Forerunner code. They were beginning to suspect it was not an ancient voice at all. It was something quite recent... and it was calling for help.”
— Mission summary