Incidentally, the first "reconcentrados" were set up by General Valeriano Weyler in Cuba in 1895.
Although a different name was given to their precursor equivalents during the American Civil War/ War between the States/ Aggression from the North/ the Late Unpleasantness.

But I don't think Baden Powell was involved with them, either. By the turn of the century he was, apparently, a bit preoccupied with cross-dressing for Tea Dances on Sunday afternoons; truly a multitalented polymath, like many Edwardians.

Cheers, Rowan