You have a strong prose style, clean and clear (well, with the exception of the misuse of the word worse in the first sentence when you meant worst—you'll probably want to avoid shaking your readers' faith in you right out of the gate). You have what I'd call a journalistic style, which, considering that this is presented as a journal entry, might be considered a finely tuned perception of the obvious. The question I have for you is this: Really? Is a journalistic accounting of events all you aspire to, given the profoundly dramatic potential of your setting and set-up?

Here's the problem with journals: like the real life events for which they serve as analogs, there are no stories in them, just stuff happening. This happens, then that happens, then something else happens. Stories take place when the random data of real life gets filtered through the mind of an artist and a narrative arc is discovered. In real life, this usually happens after the fact, when we pause to reflect on past event and think, "Well, it all worked out for the best," or "The bastards got what was coming to them." Things like that. A faith-based world view might discern the mysterious ways of the Lord at work. In a story, this process of interpretation needs to be engineered into events from the outset. It is the force field that gives purpose and direction to all that takes place on the surface, a transition from Point A to Point B and the changes that result. It's all that "What's it about?" stuff. Stories aren't just a sequence of events, they are events that happen to actual characters, and how those characters are compelled to respond. That's what is missing here.

Okay, okay, maybe you really want nothing more than to present a few pages from an actual journal. Far more likely is that you wish to use the journal format to tell a story in the first person, with the immediacy that such an approach allows. If so, there are a couple of elements you should consider (or reconsider) as you proceed.

First of all, there's the old dichotomy between showing and telling. Despite flawed advice to the contrary, both are crucial to an effective narrative style. Telling is how you move characters from one setting to another without detailing every intersection, traffic light and roadside attraction. Telling is how you avoid forcing your characters to talk in the boring, near-incoherent sentences that tend to make up actual conversation in the real world. Telling is also how you avoid forcing your characters to remind each other about things they both know, and both know the other knows, simply to spoon-feed information to the reader.

Showing is what you use when a scene is important, when a conversation is crucial to an understanding of a character's mental or emotional state, when you want to involve your reader in events. You blow past several opportunities to step out of the way and give your characters center stage, letting them reveal the events to the reader rather than simply having you tell us that the events took place. You come close to this at the end when your main character is on his own, facing the enemy soldier. You toy with the idea of showing us the reality of combat, but you dispense with all the unpleasantness in a single sentence, whereupon the calvary shows up and saves the day. Elsewhere, it seems that you might move in for a close-up treatment of the process of selecting the eleven men for the mission; dropping into a jungle from helicopters might also present you with some dramatic tension. You know what that is, right? It's what prompts your reader to wonder, "What's gonna happen next?" Trigger that response, they'll remain your readers, at least until they determine that the answer is "Not much." Here's how you dispose of that dramatic potential:

I selected eleven of my men for this mission, primarily those who appeared more rested than the others; therefore we barely needed two of the adorable choppers. Within two hours we were rappelling down long bumpy ropes into thick jungle canopy.

There is more at stake than simply an opportunity to add descriptive language. What you deny yourself is the opportunity to present your characters with problems that need to be addressed. Problems are your stock in trade. No problems, no story. Your characters have myriad problems, none of which you really use as plot points.

Here's an example of a failed story template:

Problem identified > problem solved > end

Note the absence of anything that might prompt the reader to wonder what's going to happen next. While there's a "next" in your narrative, it doesn't rise out of your characters' interactions, it's simply part of all the things you are telling us.

Here's a much more effective story template:

Problem identified > decisions made > actions taken > unexpected consequences, unintended implications > further decisions > further actions > more unexpected consequences...

And so on into the night, for as long as you can spin out plot points. I can't tell you what you should have done here, to create something akin to the second template—it's not my story, after all, and the possibilities are endless. But you're going to have to break through the bland narrative buffer that now separates the reader from the bulk of the action and discover the tensions, instabilities and problems inherent in the circumstances you've presented, and allow those to fuel an actual plot.

And then, there's your main character. What's his story? Note that this is not to be confused with the things you have him do. His story, such as it is, is what will provide the reader with the psychological / emotional entry point to your story and give them someone with whom they can identify. What is his issue? What is the disruption in the status quo, however that's defined in his life, that needs to be remedied? What drives him? You hint at this, both with your title, and when he says,

This is my third tour of duty in the bush, and I already have enough experience to qualify as a Company Commander. Sergeants are not officers, unfortunately. Our rank system is based on the old European system, wealth, not the Roman Centurion system, ability.

But nothing comes of it. Just like nothing comes of the fact that the men are exhausted and possibly not performing at their best. Truth is, there's a great story buried in these details. Figure out what it is, cut the filler in the beginning and get down to the serious business of storytelling. You'll keep your readers reading.