[3] In December 1850, Sackett returned to West Point as Assistant Instructor of Cavalry Tactics, serving until April 1855.

With the rank of captain in the 1st U.S. Cavalry, he went to Kansas Territory to Fort Leavenworth and served on various expeditions against hostile Indians.

He held that position until August 1861, when he was reassigned as the Mustering and Disbursing Officer for New York City until December, spending much of his time helping to organize newly recruited troops.

He then served on a variety of military boards (helping to organize the Invalid Corps) until April 1864, when he was sent to the Western Theater on inspection duty for the Departments of the Tennessee, Cumberland, Arkansas, and New Mexico.

[4] After spending a year in New York City awaiting orders, Sackett was sent to the Montana Territory on an inspection tour, and then went on to the Pacific Coast.

It served as a temporary prison for free state advocates, including Governor Charles L. Robinson, during the Bleeding Kansas issue in 1856.