The introduction, with the long dialogue between unseen speakers about a planetary observation, reminded me of the classic sci-fi short story 'They're Made Out of Meat', and I wish you'd carried on in the same manner because it was very well-done and served to set up the scenario very well.

I did find the details hard to follow; the perspective change between the two ships, as well as the return to the ship in orbit, was hard to follow. In particular, watch that you don't use pronouns back-to-back to refer to different people or groups without making the change of referent clear.

The concept of undead as bacteriological contamination was an interesting one, and for any OPR fan the idea of skeletal undead Battle Brothers is a great mental image, but I think you could have focused more on the unconventional weapon. But nicely done overall!

Grim as grim goes ;)