As an active duty member who has deployed, but not been in combat (I work in comm), you will be issued a multi-tool, which will be your go to item for many things. Your knife will be used for EDC kind of tasks, hardcore tactical stuff is highly unlikely, and you will be issued proper tools for that if its part of your job out there anyway (maybe invest in a widgy bar just in case). For a pure knife, I would go with ease of use, and easy pocketability.
A Mini-griptilian can be had for right at $60 on a certain coupon oriented knife site, or even a mini-presidio ultra, which has a slightly bigger handle. Axis lock works well with sand and dust, and is IMO the easiest to deploy and put away kind of lock. They Spyderco slipits are pretty good for speed, and they are pretty cheap, the FRN models are all under $40. They don't lock, but barring trying to pry like crazy or something, you don't really need a lock for what you will be doing there (and if you do, you can just use your multitool anyway).