On April 12, 1864, Forrest's men, under Brig. Gen. James Chalmers, attacked and recaptured Fort Pillow. Booth and his adjutant were killed in the battle, leaving Fort Pillow under the command of Major William Bradford. Forrest had reached the fort at 10:00 am after a hard ride from Mississippi, and his horse was soon shot out from under him, causing him to fall to the ground. He then mounted a second horse, which was shot out from under him as well, forcing him to mount a third horse. By 3:30 pm, Forrest had concluded that the Union troops could not hold the fort, thus he ordered a flag of truce raised and demanded that the fort be surrendered. Bradford refused to surrender, believing his troops could escape to the Union gunboat, USS New Era, on the Mississippi River. Forrest's men immediately took over the fort, while Union soldiers retreated to the lower bluffs of the river, but the USS New Era did not come to their rescue. What happened next became known as the Fort Pillow Massacre. As the Union troops surrendered, Forrest's men opened fire, slaughtering both black and white soldiers. According to historians John Cimprich and Bruce Tap, although their numbers were roughly equal, two thirds of the black Union soldiers were killed, while only a third of the whites were killed. The atrocities at Fort Pillow continued throughout the night. Conflicting accounts of what actually occurred were given later.
Forrest's most decisive victory came on June 10, 1864, when his 3,500-man force clashed with 8,500 men commanded by Union Brig. Gen. Samuel D. Sturgis at the Battle of Brices Crossroads in northeastern Mississippi. Here, the mobility of the troops under his command and his superior tactics led to victory, allowing him to continue harassing Union forces in southwestern Tennessee and northern Mississippi throughout the war. Forrest set up a position for an attack to repulse a pursuing force commanded by Sturgis, who had been sent to impede Forrest from destroying Union supply lines and fortifications. When Sturgis's Federal army came upon the crossroads, they collided with Forrest's cavalry. Sturgis ordered his infantry to advance to the front line to counteract the cavalry. The infantry, tired, weary and suffering under the heat, were quickly broken and sent into mass retreat. Forrest sent a full charge after the retreating army and captured 16 artillery pieces, 176 wagons and 1,500 stands of small arms. In all, the maneuver cost Forrest 96 men killed and 396 wounded. The day was worse for Union troops, who suffered 223 killed, 394 wounded and 1,623 missing. The losses were a deep blow to the black regiment under Sturgis's command. In the hasty retreat, they stripped off commemorative badges that read "Remember Fort Pillow" to avoid goading the Confederate force pursuing them.
One month later, while serving under General Stephen D. Lee, Forrest experienced tactical defeat at the Battle of Tupelo in 1864. Concerned about Union supply lines, Maj. Gen. Sherman sent a force under the command of Maj. Gen. Andrew J. Smith to deal with Forrest. Union forces drove the Confederates from the field and Forrest was wounded in the foot, but his forces were not wholly destroyed. He continued to oppose Union efforts in the West for the remainder of the war.
Forrest led other raids that summer and fall, including a famous one into Union-held downtown Memphis in August 1864 (the Second Battle of Memphis) and another on a major Union supply depot at Johnsonville, Tennessee. On November 4, 1864, during the Battle of Johnsonville, the Confederates shelled the city, sinking three gunboats and nearly thirty other ships and destroying many tons of supplies. During Hood's Tennessee Campaign, he fought alongside General John Bell Hood, the newest commander of the Confederate Army of Tennessee, in the Second Battle of Franklin on November 30. Facing a disastrous defeat, Forrest argued bitterly with Hood (his superior officer) demanding permission to cross the Harpeth River and cut off the escape route of Union Maj. Gen. John M. Schofield's army. He eventually made the attempt, but it was too late.
After his bloody defeat at Franklin, Hood continued on to Nashville. Hood ordered Forrest to conduct an independent raid against the Murfreesboro garrison. After success in achieving the objectives specified by Hood, Forrest engaged Union forces near Murfreesboro on December 5, 1864. In what would be known as the Third Battle of Murfreesboro, a portion of Forrest's command broke and ran. When Hood's battle-hardened Army of Tennessee, consisting of 40,000 men deployed in three infantry corps plus 10,000 to 15,000 cavalry, was all but destroyed on December 15–16, at the Battle of Nashville, Forrest distinguished himself by commanding the Confederate rear guard in a series of actions that allowed what was left of the army to escape. For this, he would later be promoted to the rank of lieutenant general on March 2, 1865. A portion of his command, now dismounted, was surprised and captured in their camp at Verona, Mississippi on December 25, 1864, during a raid of the Mobile and Ohio Railroad by a brigade of Brig. Gen. Benjamin Grierson's cavalry division.