In the late northern hemisphere summer of that year, Greene and Campbell began recruiting cavalry companies in southern Missouri, the former under the authority of the Confederate Secretary of War.
[1] Elements of the regiment saw their baptism of fire on 7 November when they joined Colonel John Q. Burbridge's Missouri cavalry brigade in an assault on a Union outpost near Clark's Mill in Douglas County.
Greene took command of the brigade after Porter was mortally wounded at Hartville, leading it in Marmaduke's second raid into southeast Missouri in late April, in which the regiment did not "closely engage" the Union troops.
[1] The combat service of the regiment in 1864 began with skirmishing between 31 March and 15 April, attempting to delay the advance of the army of Union Major General Frederick Steele during the Red River Campaign.
[2] During late May and early June, the 3rd Missouri Cavalry harassed Union shipping on the Mississippi River from positions on the west bank in Chicot County, Arkansas, sinking, burning, disabling, or damaging several boats.
On 6 June it fought in the Battle of Ditch Bayou, forming part of the main Confederate line and delaying the Union advance over several hours.