Very well-written actually. It's a step above what I'm used to expecting from the random guy wanting to do some fan-fic. You take any writing classes? The only reason I ask is that one of the most common mistakes people make is breaking POV and you keep us firmly rooted in Tuke's head the entire time. It was just a quick reading, but I don't think I noticed a single POV slip.
You do use "instantly" at one point and I have an aversion to all "-ly" adverbs, but you do a good job of using strong verbs throughout, so I think one or two is okay.
Only a couple things I'd change.
having just climbed up the edge of the crater.
The rest of the passage is entirely in... sort of "real time." Even though all the wording is technically past tense, we're getting info "as it happens" (or in the order is happened). In this line though, you directly reference something the soldiers just did rather than what they're doing. It kind of pulls us mentally out of the "flow" you've gotten us into. If you can find a way to give us something in the "present" to let us infer the past the flow isn't broken. Maybe one soldier is giving the last one a hand up?
Tuke was almost thrown off of his feet
Tuke almost snapped to attention
It's always better to "show" than "tell." You pretty much show us what's happening in the rest of the passages, but in these two spots you slip up a little and just tell us. Rather than talking about what "almost" happened, show us what actually did happen. You can achieve much stronger imagery this way. Saying Tuke was almost thrown off his feet is very passive, because technically the sentence only tells us what
isn't going on. Despite the presence of an explosion there's no action! Instead, you could mention him bracing himself or struggling to regain his balance. Likewise, instead of simply not saluting, have him "fight the urge to snap to attention." Stronger, more active sentences draw us in much more than passive ones.
Really though, quality writing, I'll be waiting for the next piece.