 He received a commission as a second lieutenant in the U.S. 7th Cavalry Regiment upon graduation and was first sent to Fort Leavenworth in Kansas, then Fort Wallace and Fort Harker, also in Kansas.He participated in "The Plains" Indian warfare from 1869 to 1876 and also served "Ku Klux" duty in the South, according to a comrade, during the post-Civil War Reconstruction Era when Porter served in various cities between 1871 and 1873, including Chester, South Carolina, Rutherfordton, North Carolina, Lincolnton, North Carolina and then Shelbyville, Lebanon and Louisville, Kentucky while the 7th was charged with suppressing the Ku Klux Klan.For his efforts in serving "Ku Klux" duty, Porter was recognized by a comrade for his "energy and discretion [which] formed a combination sufficiently rare and valuable to give him a name among his fellows."