But Edward E. Leslie, author of “The Devil Knows How to Ride: The True Story of William Clarke Quantrill and His Confederate Raiders,” said Quantrill’s legacy is neither all-good nor all-bad.

Audie Murphy plays a young Jesse James falling under the Svengali-like spell of the outlaw William Quantrill, played by Brian Donlevy. Jesse and his youthful gang join the rebels to avenge the ...