On the drizzly morning of April 12, 1864, Confederate General Nathan Bedford Forrest followed the sound of gunfire and galloped toward Fort Pillow. The garrison high on the bluffs overlooking the Mississippi River 40 miles north of Memphis had been built by the Confederacy at the onset of the Civil War but captured by the Union in 1862. Now, after spending weeks destroying Union supply lines in daring cavalry raids throughout Kentucky and western Tennessee, Forrest’s men were attempting to take back the fortification named after Confederate General Gideon Johnson Pillow.

Although he had no formal military training, Forrest, who had been a slave owner and trader before the war, had risen from the rank of private to lieutenant colonel in less than five months after enlisting in 1861. At Fort Donelson, Shiloh, Chickamauga and other battles, the man nicknamed the “Wizard of the Saddle” had proven to be a brilliant cavalry leader and keen tactician. Union General William Tecumseh Sherman called Forrest “the very Devil,” while noted Civil War historian Shelby Foote wrote that Forrest and President Abraham Lincoln were the “two authentic geniuses” of the Civil War.

Forrest put his battlefield success in much simpler terms, however: “To get there first with the most men.” And on this damp April day at Fort Pillow, the Confederate general had just that, an estimated 1,500 troops against approximately 600 Union troops, including 262 African-American members of the U.S. Colored Troops, inside the citadel under the command of Major Lionel Booth.

The Confederate forces pressed their advantage from the firing of the first shot, and early in the battle a sharpshooter mortally wounded Booth. At 3:30 p.m., the guns fell silent as Forrest dispatched a message to the enemy: “I demand the unconditional surrender of the entire garrison, promising you that you shall be treated as prisoners of war. My men have just received a fresh supply of ammunition, and from their present position can easily assault and capture the fort. Should my demand be refused, I cannot be responsible for the fate of your command.” Major William Bradford, who had assumed command, asked for an hour to make a decision. Fearing the arrival of reinforcements, Forrest gave them 20 minutes. Bradford refused to surrender, and Forrest’s men sounded the charge and quickly stormed Fort Pillow.

What happened next is still debated today. Union soldiers made the claim that, although they laid down their guns in surrender once the fort was overwhelmed, Confederate soldiers killed dozens of unarmed troops rather than take them as prisoners of war as protocol dictated. Forrest’s men claimed that the fort’s occupants had continued their resistance and had been killed in self-defense in the course of battle.

The Union pointed to the death count to press their claim. While the Confederates lost just over a dozen men, upwards of 300 Union troops were killed. African-American Union soldiers suffered a death rate of 64 percent, while the death rate of their white counterparts was half that. Union survivors reported that a slaughter had occurred, and that African-American soldiers were shot, burned and drowned as they attempted to surrender.

Northern newspapers printed stories of atrocities from what they called the “Fort Pillow Massacre.” The Chicago Tribune reported the Confederate fighters “cruelly butchered every colored soldier they could lay hands upon.” Southern newspapers such as the Atlanta Appeal published the “correct history of the facts connected with the capture of Fort Pillow” that “gives the lie to the Yankee stories of ‘brutal massacre.’”

Congressional investigators interviewed survivors and concluded that Forrest’s men engaged in an “indiscriminate slaughter” in “a scene of cruelty and murder without a parallel in civilized warfare.” Confederate Sergeant Achilles Clark appeared to corroborate that story when he wrote home shortly after the battle: “The slaughter was awful—words cannot describe the scene. The poor deluded Negroes would run up to our men, fall upon their knees, and with uplifted hands scream for mercy, but they were ordered to their feet and then shot down.”

In the wake of the battle, the Union refused to participate in further prisoner exchanges, and African-American units charged into battle with the rallying cry “Remember Fort Pillow!” After the Civil War, Forrest reportedly became the first grand wizard of a newly formed secret white-supremacist organization fighting Reconstruction, the Ku Klux Klan, although he denied association with the group before Congress.

The debate over what happened at Fort Pillow, and even whether to call it a “battle” or a “massacre,” still simmers 150 years later, and at times the controversy bubbles over, particularly when in regards to Forrest. Although Clark recounted that “Gen. Forrest ordered them shot down like dogs,” defenders of the Confederate general argue that no evidence exists that he ordered a massacre. An historical marker in Tennessee says Forrest “lost control over his troops,” while Foote wrote in his account of the Civil War that Forrest did “all he could, first to prevent and then to end the unnecessary bloodshed.”

Protests have been raised over honors bestowed upon Forrest, whose name adorns schools, parks and public buildings in the South. Civil rights activists have protested plans in recent years to erect a new monument to Forrest in a Selma, Alabama, cemetery and issue specialty license plates in his honor in Mississippi. Last year, the Memphis city council sparked a lawsuit when it voted to remove Forrest’s name from a park where he and his wife are buried under a bronze equestrian statue of the Confederate general, which is often defaced. Meanwhile, one thing is clear: The guns may have fallen silent at Fort Pillow 150 years ago, but the battle over its history still rages.