Its cavalry regiments were active units, but most of the support elements were "Regular Army Inactive" (RAI) units manned with Organized Reserve personnel.

The division never assembled in a single location or conducted large-scale training, and was disbanded on 10 October 1940.

[1] The 3rd Cavalry Division was constituted in the Regular Army on 15 August 1927, allotted to the Fourth, Sixth, Seventh, and Eighth Corps Areas, and assigned to the Second Army.

The division was reassigned to the General Headquarters Reserve (GHQR) as a result of the US Army reorganization of 1933.

The 3rd Cavalry Division's designated mobilization station was Fort Des Moines, Iowa, where many of the division’s units were organized with Reserve officers as RAI units and where most of them conducted their annual summer training camps.