From the Secrecy News blog (FAS) - Army Civil Affairs Operations.

Civil Affairs has recently been elevated to a branch of the U.S. Army by order of Army Secretary Francis J. Harvey on January 12, 2007.

The role of civil affairs is to support "the interaction of military forces with the civilian populace [in or around the battlefield] to facilitate military operations and consolidate operational objectives."

According to an Army manual on civil affairs operations (Civil Affairs Operations, U.S. Army Field Manual FM 3-05.40, September 2006), "A supportive civilian population can provide resources and information that facilitate friendly operations. It can also provide a positive climate for the military and diplomatic activity a nation pursues to achieve foreign policy objectives."...