There has long been conflict between the State Department and the Department of Defense over who is in charge when the United States is trying to bring order to some overseas mess. The Department of Defense has the most personnel and material. But the State Department is permanently in charge of dealing with foreigners, and mutual problems the United States might have with them.
In effect, ARC members are diplomats who use their skills with other members of the U.S. government, as well as with foreigners. In the past, the State Department had a reputation for not playing well with other branches of the American government. ARC is meant to overcome that, and help quickly bring to bear all American resources available to deal with overseas crises. In addition to solving these problems, ARC makes all branches of the U.S. government feel good about a job well done, instead of grousing over opportunities lost.
The U.S. State Department is increasingly thinking like the Department of Defense. Case in point is its new effort to create a 'rapid reaction force' for overseas emergencies. It's called the Active Response Corps (ARC), and consists of diplomats trained, and equipped, to quickly go to some hot spot and immediately collect information and coordinate the efforts of other U.S. government agencies. There are ten diplomats in ARC now, and there will be at least thirty by the end of next year. Members of ARC are selected for their experience in crises type situations, and their willingness to jump into another one on short notice. ARC members are sent individually, or in small groups, to crises situations, and stay for as long as six months.