Michael:
Although you did not say what truck you have, I'm presuming it's a 3rd-gen diesel. I'm also going to guess that you're placing it into typical military POV storage (open storage in a large parking lot, either on a military installation or with a contractor).
Wash and wax the truck, IOT protect the finish to the extent that you can. Put an appropriate amount (read the label) of a good diesel fuel treatment such as Stanadyne or PowerService in the tank, and then fill the fuel tank to minimize the amount of air available in which condensation can occur. IF YOU CAN, put the vehicle up on blocks or jackstands to relieve pressure on the tires. Set an auto Xmsn in "P" or a manual in gear, DO NOT set the parking brake; chock the wheels unless you have it up on blocks. Disconnect the batteries, and if possible, find somewhere to store them indoors at room temperature. If you aren't able to do that, then just disconnect them and plan on buying two new batteries when you return. Go buy a box of those drier sheets (Bounce or similar) and toss a half-dozen wadded-up sheets around the interior of the cab. Keeps out insects and vermin; no I don't know why, it just works. Consider plugging-up the exhaust pipe and air intake so that you don't get mouse nests in there. Remove all valuables except perhaps an adjustable wrench to help you get the batteries re-installed. Personally, I would not add straight coolant, but keep the 50/50 mix that you currently have there. If you're really concerned about it, you could try draining the coolant (but remember to add some when you return). And leave a note inside the cab detailing all that you did, so that you remember to un-stuff the exhaust pipe and air intake in case you don't remember to do that 12-15 months from now. This will also help if things go badly and someone else has to retreive the vehicle from storage.
Park the beast, pat it on the hood, take the keys and walk away. Don't forget to call your insurance company and tell them that it's in storage, and have them reduce the coverage down to comprehensive and towing / emergency service only while you're gone and to reduce the premium by eliminating the liability and collision insurance that you won't need while you're away. (Of course, remember to turn this back on shortly before you redeploy so that you're covered when you pick it up). The reason that I mention leaving the emergency road service in force is so that they can come help you if you need it immediately upon return, and besides it's usually only $2-3 / month. If you still owe money on the truck, call the lender and inform them that you are going on deployment; they may cut your interest rate.
If storage is at a contracted POV storage facility, they will probably offer you the option (at your cost) to start the truck up and run it around every week or two. Think about this very critically, and consult with SJA and other soldiers concerning the reputation (and prior claims against) the contractor. Do you REALLY want some stranger driving around in your pride and joy? Prior to my last deployment, there were a number of claims against the contractor for in-storage damage, so I declined this particular extra-charge service. Do a really good inventory of the truck and its condition during the turn-in procedure, as this will be used for the basis of any claims should damage occur while in storage. They'll probably make you turn in a key; remember to keep a spare in case they lose it.
I went through the same process about four years ago for my own all-expense-paid vacation to the sandbox. Only difference was that mine was stored in the SE (Ft Stewart) with less exposure to low temperatures and much higher humidity. The truck sat in a military-contracted POV storage lot (i. e. , sitting on gravel and not messed with) for a bit over a year. It only took a jump to re-start it, and then replacement of both batteries later that day. It did run just a tad rough until the next fill-up. The tires managed to last another year. During several previous deployments I'd stored gassers using much the same procedure except Stabil instead of diesel fuel additive. In one case with private storage (barn) available, I also drained the oil and coolant, but left a note to add it back before attempting to crank. Something to consider depending on your exact circumstances.
Then go deploy with one less set of worries to distract you from your duties. Just remember that you're headed to a region of the world with a strong tribal-based society where loyalties can be bought and sold. Do not trust ANYONE who is not a US soldier, sailor, Marine, or airman. Good luck and Godspeed to you.
Attention: TDR Forum Junkies 
