ARLINGTON, Va. (AP) — When Paul Davis heard earlier this year that the complete remains of two Civil War soldiers had been uncovered recently at Manassas National Battlefield, mixed among severed limbs in a surgeon's pit, he immediately wondered: Could that be his great-great uncle William, who died at the Second Battle of Bull Run, but whose bones had been lost to history?

From what he knew of his ancestor's death, it seemed possible. Davis had read letters that said William — a color sergeant in the 2nd Wisconsin Infantry Regiment, part of the Union Army's famed Iron Brigade — died after bei...