If you are deploying
A car that sits for months needs a plan, not just a parking space. Talk to your insurer before you go — most will adjust coverage on a stored vehicle rather than have you pay for a policy you cannot use. Give someone you trust the legal authority to act for you, so registration, inspection or a payment can be handled without you. Fuel stabilizer, a battery tender and correct tire pressure prevent most of what goes wrong in storage.
Federal law — the Servicemembers Civil Relief Act — gives you specific rights on debt taken on before you went on active duty, and on some vehicle leases when you deploy or receive orders. It is worth reading, and the legal assistance office on your installation will go through it with you at no cost. That is true wherever you buy.
The other side of a deployment is what you come back to. Money set aside while you were away is the strongest down payment there is: it lowers what you finance, shortens the loan and cuts what you pay in interest. If you are planning to buy when you return, that is the thing to protect.