Last December, the president of South Korea ordered his military to organize a joint command for forces guarding the west coast area near the North Korean border. This was in reaction to a recent North Korean artillery attack on a South Korean island just off the coast and near the maritime border. But the navy and air force commanders killed the plan by invoking South Korea's constitution, which gives joint command only to the chairman of the joint chiefs of staff. Each service (army, navy and air force) is commanded by a chief of staff, who has sole control over his service. The president backed down, even through the U.S. has a similar system of service chiefs, and a chairman of the joint chiefs of staff, and still has many joint commands. Unlike the United States, the South Korean military is not yet willing to lets its command systems evolve.
The U.S. armed forces have been constantly evolving new ways to command troops in combat. Beginning after World War II, American generals and staffs were assigned responsibility for military emergencies in different parts of the world. When there was a crisis, the CINC (Commander in Chief) of that region would be in charge of whatever American forces were sent to the area to take care of the problem. Through the 1980s and 90s, procedures, laws and military organizations were changed to make it easier for the CINCs to deal with all those different forces. A CINC has always been expected to expertly deploy navy, army, air force and marine forces. For decades, this meant having the commanders from each of those services decide how they would operate. But this often caused disputes over who should do what when. The CINC often found himself in the middle of service rivalries that were causing him more grief than the enemy.
The solution, has been to think jointly (or "purple"). Since the 1980s, the Department of Defense has been pushing real hard for everyone to think Purple (what was good for everyone) rather than just concentrate on what was best for their particular service. Each service tends to believe that they are the essential ingredient for military success, and that the other services are just playing a supporting role. It's taken a generation, but there are now more Purple generals than those in various shades of green and blue (the colors of the uniforms in the different services that, when merged, are purple.) The South Korean's know about the whole "purple" business, but are not yet ready to go there.
The signs of the passion for purple are everywhere in the United States. During the 1990s, the air force reorganized its combat units into Air Expeditionary Units, AEFs). Each is a miniature air force, with combat and support aircraft and the troops to maintain them. Several are trained and ready to quickly move to an overseas hot spot on short notice. When a CINC needs air power, the air force asks him how many AEFs he needs.
The navy had always been organized into task forces, but it also had a long tradition of going it alone. After all, the navy has warships, warplanes and its own army (the marines.) For the last half century, most crises have not involved the risk of a large war, and were small enough so that the navy thought it could do it all. That has changed, as CINCs became less tolerant of the navy's independent ways. Several admirals balked at thinking purple during the 1991 Gulf War, got chewed out for it, and after that the navy started to take purple seriously. But the Gulf War demonstrated another reason for the navy to get purple. That war required a lot of aerial refueling for navy warplanes, and this required air force tankers. Congress has shown no enthusiasm for buying a fleet of aerial tankers for the navy, so the navy has to be nice to the CINC, who can order the air force to refuel the carrier aircraft.
The army has always been the most purple of the services, because, more than any other service, the army is the one you can't do without. The army came first, before ships and aircraft. But now the army is undergoing an evolutionary change brought about by rapidly evolving technology. UAVs, more spy satellites and vidcams at the front have shown that there are too many levels of headquarters between the brigades (which do the fighting) and the CINC (who is running the show.) Put four divisions into an area and the army will bring along an army headquarters, two corps headquarters and four division headquarters to supervise the activities of 15 or so combat brigades. During the Iraq campaign, the CINC found it counterproductive to go through an army, corps and division headquarters to tell a brigade commander he wanted something specific done, right now. And often the CINC just bypassed all those headquarters. So now the army has been eliminating some of those headquarters. If they don't, CINCs will simply continue to ignore the redundant headquarters, creating more embarrassing situations and, ultimately, Congressional unwillingness to pay for headquarters that just get in the way.
The army could see this coming with what the marines have been doing for the last few decades. The marines have gradually reorganized themselves into battalion and brigade sized expeditionary forces. There was no way to avoid this, since there were a limited number of amphibious ships and the marines had to be prepared to go ashore with everything they needed for up to 30 days. The marine divisions still exist, mostly on paper. When needed, the marines gather together enough battalions and brigades to form a division and that's that. The army is larger, with 18 active and reserve divisions (compared to three marine divisions.)
In South Korea, the problem was that the navy and air force saw themselves playing a major role in dealing with North Korea off their west coast, and feared that an army general acting as CINC would result in a commander unfamiliar with what the navy and air force can do. That's a good point, and the solution is to train CINCs who can think purple. But even in the United States, that means giving the CINC a staff of experts from each of the service who can quickly let the boss know what each of the services can do in a particular situation. But for the moment, South Korea still has a major problem with none of the services willing to give up much authority or autonomy, except at the highest level.