I agree with most of the comments above. War stories are much more interesting when there is some moral ambiguity, but this didn't have any. It could have taken place just as easily in Vietnam or Iraq.
The short and similarly structured sentences got repetitive.
It felt like there was a cheat with the "organics." The author dropped us into the world without explaining anything, making us play catch-up, which I do not have a problem with. We knew that the soldliers had not found any organics after being in this place for a long time. Then they come across those girls in the tunnel, and they all know that they have found organics. Why? Well, since I've been left in the dark about most details in the story, I assume that the author has something in mind. If organics can be easily and obviously detected, the soldiers wouldn't bother explaining how they knew about them in a story like this. Fine. But the kicker at the end is that the girls didn't have organics. So why did the soliders think they did? Why isn't there a test if these things are so important? This felt like a cheap way to have a solider cut open a poor little girl for no good reason.
This led me to a bit of a Writer's Insight. If you are writing a story in which details are going to go over the reader's head, you still need to keep track of them yourself. The reader is trusting you to. "Ah-hah. Tricked you! You thought there were organics in the girls, didn't you." Well, only because you told me there were. The reader puts trust in the author in a story like this than in a regular story where everything is explained.
Though I did think that, while so much military SF is full of super-powerful soliders, the weakness of these soldiers was interesting. Instead of power armor they wear "slicks" and instead of megawatt plasma rifles, they use "spray." Two of the soliders are killed by stick-figure villagers with rocks and bugs. I wonder if the soldiers were weak because of the frailty of the people they are fighting. Had soldiers become weaker and weaker over the years as civilization declined? Or was it just in this one case? I don't know if this was intentional, but it was an aspect of this world that I thought was interesting.