I came across several things in General Order 100 signed by President Lincoln titled “Instructions for the Government of Armies of the United States in the Field”, which can be found here. Article 50 states:
“Moreover, citizens who accompany an army for whatever purpose, such as sutlers, editors, or reporters of journals, or contractors, if captured, may be made prisoners of war, and be detained as such.
The monarch and members of the hostile reigning family, male or female, the chief, and chief officers of the hostile government, its diplomatic agents, and all persons who are of particular and singular use and benefit to the hostile army or its government, are, if captured on belligerent ground, and if unprovided with a safe conduct granted by the captor's government, prisoners of war.”
My question is what is belligerent ground? It seems to have some technical usage here that I can’t seem to find elsewhere. “ belligerent ground” is typically used in the context of “belligerent ground forces.” Can anyone help me out?