Thirteen dead Spartans
From Halopedia, the Halo wiki
The bodies are those of presumedly SPARTAN-IIIs and are scattered around the landscape. Their armor is randomized, with different configurations and genders every time the level is loaded. The fact that there are thirteen of them may be a reference to the number seven, as at the end of their last stand Noble Six becomes the fourteenth dead Spartan in the area.
The Spartans' mission is unknown. They were assumedly deployed to fend off the Covenant attack on the Asźod territory near the ship breaking facilities. The team may have included all or part of Red, Gauntlet and/or Echo teams, as all three teams were present on Reach during the invasion.
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