The U.S. is facing a real crises trying to find enough interpreters for operations in Afghanistan. Three years ago, the U.S. had only about 700 Afghan (Pushtu or Dari) linguists. Next year there will be five times as many U.S. troops in Afghanistan as there were in 2006. Unlike Iraq, where you can draw interpreters from the entire Arab world, there are far fewer Pushtu and Dari (an Iranian dialect) speakers to draw from.
Then there are the dialects. This was a problem in Iraq, where interpreters from other Arab countries had to master the Iraqi dialect before they could be entirely effective. These dialects are similar to those in any language. Americans who have travelled their own country have found a wide variety in the way English is spoken. Travel to other English speaking countries (England, Scotland, Ireland, Australia, and even India, where there are more English speakers than in all of Britain) and can see how difficult the dialect problem is. There are many dialects in Afghanistan, mainly because the country has poor communications (few roads or navigable rivers, no railroads and not a lot of air travel), and most people live their entire lives in a small area, making their local dialect more distinct from all the others. This turns out to be a major problem in Afghanistan, which has more local dialects than Iraq, and more of them are initially incomprehensible to people from distant parts of the country. This increases the possibility of misinterpretation, and that can be very dangerous when you are trying to obtain information, or win new friends.
The Department of Defense can't train enough new military interpreters, so it has to hire local people. That is difficult in Afghanistan. The problem is that the local terrorists realize that the interpreters are important, and they, well, terrorize the interpreters into quitting or, even better, becoming a terrorist spy. This, obviously complicates things for the combat troops who need the interpreters to get their work done. The solution has been to have the intelligence troops work closely with hiring and monitoring interpreters. In some parts of Afghanistan, the interpreters are hired in secret, and much effort goes into keeping their job status secret from the local community.
Although the U.S. military has about 17,000 troops who speak languages like Arabic, Chinese, Farsi (Iran), Urdu (Pakistan), Hindi, and Korean, there simply aren't enough for operations in Iraq and Afghanistan. Meanwhile, the Department of Defense has established the Civilian Linguist Reserve. Those who qualify (in terms of skills, and ability to get a security clearance) would be paid a monthly fee to be available, in an emergency, to come work for the military. The Pentagon found a lot of American Arabic speakers during the Iraq war, because these civilians went to work for contractors, or directly for the government, to provide translation services in the United States and Iraq. Many of these interpreters are already qualified for the Civilian Linguist Reserve. Same thing with Americans who can speak Afghan languages. Many more of these Afghan-Americans are being sought to travel to Afghanistan and serve as interpreters. The pay is very good, but there is some danger, and that discourages some potential volunteers.
There is another problem with Afghanistan, and that is the low level of literacy. The Taliban still generate lots of internal documents to be captured, but there are fewer English speaking Afghans you can recruit to translates captured material. The translators are also needed to translate American military and technical texts into local languages. Unlike Iraq, where there were many university graduates who understood English, there are far fewer such people in Afghanistan. Much of the translation has to be done in the United States, or other countries where you can hire literate, bi-lingual Afghan expatriates for the work.
The rarest, and most valuable, Afghan linguists are those who are American citizens (and can get a security clearance) and then work on secret documents (especially true for intelligence work.) Many of these are non-Afghan American citizens who have mastered written Pushtu and Dari, but are not that fluent with the spoken version.
Locally hired interpreters make over a thousand dollars a month, which is very good money in Afghanistan. Foreign hires make about ten times that, especially if they work in Afghanistan. The U.S. is spending nearly $2 billion a year on translators and linguists, mostly for Afghanistan and Iraq.