Asher has touched the topic of language for Marines/Army in Afghanistan briefly at Registan here, I have tried to contribute my impression of it in the comments here. For my part, I can not speak of Army deployments, but in the civilian interaction on the ground in Pakistan, Xinjiang and recently Tajikistan for that area (mainly international NGO/UN staff but also private contractors and researchers). I still believe that it is way more important to get a feeling for where the person speaking in that other language is heading emotionally, with his mimics and with some words you somehow get from a language crash course than having completed a full University Pashto course back home on the language, being even able to read the local newspaper from Peshawar. You’ll only to get confused why rural people here actually don’t speak the Pashto you learned back home and not figuring how the locals ridicule you wearing a Shalwar Kameez, a skull cap and an obviously beard growing only since the day you knew you would be heading here with blending-intentions, since at your age and with your education here simply nobody does that.
An article by Guy Deutscher at the NYT provides some insight into how knowing the language will help you grasp differences in perception – or when not knowing it acknowledging that there may be such.
When your language routinely obliges you to specify certain types of information, it forces you to be attentive to certain details in the world and to certain aspects of experience that speakers of other languages may not be required to think about all the time. And since such habits of speech are cultivated from the earliest age, it is only natural that they can settle into habits of mind that go beyond language itself, affecting your experiences, perceptions, associations, feelings, memories and orientation in the world.
He elaborates on the example of languages that do not have the concept of “left” and “right” but use the geographical directions instead.
The area where the most striking evidence for the influence of language on thought has come to light is the language of space — how we describe the orientation of the world around us. Suppose you want to give someone directions for getting to your house. You might say: “After the traffic lights, take the first left, then the second right, and then you’ll see a white house in front of you. Our door is on the right.” But in theory, you could also say: “After the traffic lights, drive north, and then on the second crossing drive east, and you’ll see a white house directly to the east. Ours is the southern door.” These two sets of directions may describe the same route, but they rely on different systems of coordinates. The first uses egocentric coordinates, which depend on our own bodies: a left-right axis and a front-back axis orthogonal to it. The second system uses fixed geographic directions, which do not rotate with us wherever we turn.
I am not aware of such grave differences in outlook in any of the languages of the region, there may well be. But there are some lighter examples. In Urdu there is only one word for “yesterday” and “tomorrow” (“kal” and “parson” for the day before/after respectively), in everyday language plural may be understood as singular (“humko deewana”, ever and ever returning in Bollywood songs) and “masdoori” Pathans tend to speak Urdu only in 3rd person singular, future tense, who- or whatever they refer to.
In that respect knowing the language does give you some help to see the world more like your counterpart, which again proves helpful in communicating effectively. But again, these are not really things you learn in a language course but rather on the ground while keeping your ears open and your mind sharpened.
Update: An example slightly differing from the above reasoning in Lapata’s recent review at Bookslut:
A popular book among Western travelers to India is the DIY medical text Where There is No Doctor. There are of course many doctors in India, but the combination of frequent illnesses and an enticing over-the-counter availability of medicines often proves too tempting for many travelers. Hours can be spent perusing chapters on worms and gastro-intestinal ailments, and the reader quickly discovers in herself an endless capacity to self diagnose and slip into hypochondria. As a gift for a friend who reads Hindi and does not have access to particularly good medical care, I once purchased the Hindi version of the book. The Hindi title, Jahan Doctor na ho, differs ever so slightly from the English version, in that it uses the subjunctive. Thus, “where there is no doctor” becomes “where there may be no doctor.” The difference is subtle, but it captures nicely the fact that often there actually is a doctor, but will he be available? Will he be a good doctor? When you cannot depend on a positive answer to these questions, this is the book for you.