James McPherson addresses the Ft. Pillow Massacre in his mastertext, The Battle Cry of Freedom. McPherson considers the proof that Forest ordered the massacre conclusive. Quoting his note on pg.748:

Although formerly disputed by Southerners, the truth of a massacre of several dozen black prisoners and some whites... is now generally accepted. For summaries and analyses of the evidence, see Robert Selph Henry, "First with the Most" Forrest (Indianapolis, 1944)m 248-269l Albert Castel, "The Fort Pillow Massacre: A Fresh Examination of the Evidence," Civil War History, 4 (1958) 37-50; and John Cimprish and Robert C. Mainfort, Jr., "Fort Pillow Revisited: New Evidence about an Old Contreversy," Civil War History, 28 (1982) 292-306.