For decades, the Department of Defense had to deal with a small group of potential enemies. There was the Soviet Union (the big one) and North Korea (a relatively small bad guy). Since the Cold War ended in 1991, the number of potential foes has increased. During the Cold War, there were thousands of experts on the Soviet Union available. Some were in uniform, others came from think tanks, defense consultants and other branches of government. With the end of the Cold War, the generals and admirals found that there were far fewer experts on the nations that were now considered threats. Moreover, it's not enough just to have people on call that know a lot about Iraqis, Iranians, North Koreans, Indonesians or what have you. You also want an expert who understands the needs of the particular service seeking advice.
The army, air force and navy all seek somewhat different types of information on foreign countries. As a result of this need, many senior officers, especially in the navy, are trying to expand a military career category, foreign area officer (FAO), that has long existed only as a fringe or secondary occupation for officers. The new and improved FAO would would be a career long gig, with promotion possible up to Major General (O-8). Currently, anyone specializing in area studies will not get past O-5 (Lieutenant Colonel.)
Promotion potential is necessary to attract people to a job that requires years of work (to learn one or more foreign languages, spend time in the region and so on). Thus the FAO must be assured of career opportunities and sufficient work to keep them occupied for 20-30 years. The military has had "foreign area officers" in the past, but this was done informally to provide competent officers for the job of military attach at American embassies. Only a small number of officers were needed for this, and the ones who got the job were the ones willing to learn foreign languages (which the military would take care of, via the military language schools or by paying fees for outside study). Learning about the foreign cultures was sometimes taken care of by sending officers off for post-graduate study. But the officer has to use a lot of their time to become a foreign area officer "expert." However, these officers were not seen as career FAO. They had a regular military career path (infantryman, pilot, naval officer) and kept their foreign affairs skills as a secondary specialty.
The establishment of a career category for FAOs would attract a special kind of officer, and might only select candidates after they had been in the military for five years or so, to get their basic knowledge of military affairs. Perhaps SOCOM (Special Operations Command) would then train candidates to be FAOs, and have them spend time with the existing "foreign area experts" (Special Forces and civil affairs officers.) Indeed, prime candidates for foreign area officers would be Special Forces troops looking for additional challenges. Although most Special Forces troops are NCOs, they are carefully selected and trained, and good candidates for promotion to officer rank as FAOs. Retired Special Forces troops would be another pool of candidates, as the foreign area officers don't have to be young guys. Indeed, you want older and more experienced people in those jobs. Another likely source of FAOs will be women, who have already done excellent work in military intelligence. Since the FAOs work is closely related to military intelligence, this provides female intelligence officers another option.