Cecil Sharpe in song collecting trips to the Southern Appalachians in 1917 - 1919 collected several variants of the Cruel War. They can be found in his book "English Folksongs in the Southern Appalachians." Variants of the song are also found in the British Isles as the theme existed far earlier than colonial America. A search for the origins should begin with the song in Ireland, Scotland, England, or Wales. There are no doubt Europeon continental variants as well, but the American version is likely drawn from British Isles variants.