I believe the cavalry referred to as "Forrest's Cavalry in the Yazoo Pass operations was the General's younger brother Aaron. Gen Forrest was operating in middle Tennessee during February of 1862.

http://andspeakingofwhich.blogspot.com/2012/07/aaron-forrest-and-yazoo-pass.html
Aaron Forrest (1828-1864) was seven years younger than his brother Nathan.
Aaron joined the war effort as a soldier in the Sixth Battalion, Mississippi State Troops. With the rank of captain, Forrest commanded a cavalry company. Operating mostly as scouts, Forrest’s company was in the Mississippi Delta in the spring of 1863. It was during the Yazoo Pass Expedition that Forrest had his brief brush with infamy.