Hansford received an appointment to the United States Military Academy at West Point, New York and attended beginning in 16 Jun 1887 graduating in 1892. C\He was commissioned as a 2LT on 11 Jun 1892 to serve in B Company 13th Infantry Regiment. He participated there in rifle competition in 1893 and 2LT Threlkeld represented his regiment in the 1894 rifle competitions. In October 1894 he took a month leave. 2LT Threlkeld was detailed to serve on a Court Martial board in June 1895. He underwent an examination for promotion in 1898 and was selected in July of that year for promotion to 1LT. He was then posted to C Company 13th Infantry.
C Company 13th Infantry found itself in Manauag, Luzon, Philippines in April 1900 and 1LT Threlkeld was commanding the company and governor of Manauag. He was promoted to CPT in 1901 and assigned to the 30th Infantry Regiment. He then was detailed to recruiting duty in Cincinatti, Ohio.
Hansford's engagement to Elizabeth Berry Waller of Morganfield, Kentucky was announced in February 1902. The couple returned to Cincinnati to live. CPT Threlkeld was detailed to serve on a court martial board at Fort Crook in April 1904. Shortly after that he served on a promotion board. The Threlkelds had a son born in January 1905. Apparently continuing his interest in shooting competition in participated in service pistol competition in August 1906. Posted to the Philippines again in 1908, he was accompanied by his wife and stationed in Manila. The couple returned to the U.S. in 1909. Having graduated from the Army School of the Line, CPT Threlkeld attended the Army Staff College in August 1910. He took 3 months leave in June to August 1911 after which he was stationed with the 30th Infantry at the Presidio San Francisco, California for what was a planned 2 year assignment cut short by operational needs requiring CPT Threlkeld to go to Alaska in 1912. However this was interrupted when he became ill and was put on sick leave for several months which was extended for 2 months in July. However he was still considered for promotion in October of that year and he went to Jeffereson Barracks before he was supposed to continue to Alaska. However, after another month's leave he was instead assigned to the Columbus Barracks in Ohio on recruiting duty. He was relieved and returned to the 30th Infantry in June 1913 and promoted to MAJ in October 1914. By this time Austria-Hungary had declared war on Serbia beginning the first World War.
On 25 Aug 1915 MAJ Threlkeld departed for Plattsburg, New York to rejoin his regiment. The 30th had duty on the Mexican border in 1916 and MAJ Threlkeld was with them until he was ordered to report in September 1916 to attend the Army War College. After completing the course MAJ Threlkeld was on duty there as staff before being reassigned to the 35th Infantry Regiment. Promoted to COL sometime before November 1917. The relatively new COL took command of the 116th Infantry Regiment, just formed, from COL Leedy in January 1918 in anticipation of COL Leedy attending training at Fort Sam Houston. However, the retirement/discharge of BG Vaughan resulted in his reassignment as temporary commander of the 58th Brigade, the next higher headquarters in the 29th Division, being replaced by COL William J. Perry. After a replacement was found for BG Vaughan, COL Threlkeld returned to the 116th. He was then assigned to the 321st Infantry Regiment at Camp Jackson, South Carolina. It is unclear if that transfer ever happened. COL Threlkeld shipped out for France on 19 Jun 1918 aboard the Great Northern and he was still recorded as being assigned to the 29th Division.
Once he arrived in France he was made an Assistant Chief of Staff in which position he served until his return in 1919. Initially assigned to Plattsburg, New York barracks, he requested retirement in 1920. Hansford and his wife moved back to Morganfield, Kentucky. In 1922, President Harding appointed a number of people across the country to a committee to support the raising of funds for the relief of people in the near east and Hansford was among those selected. COL Threlkeld received a silver star device to his Spanish campaign medal in recognition for gallantry at the July 1898 battle of Santiago.
Chief among the Hansford's interests was genealogy. He was a member of the American Genealogy Society, the Sons of the American Revolution, the Filson Club and the Kentucky State Historical Society. He wrote a book, Threlkeld Genealogy, which was published in 1932. Hansford was ill for several years before dying on 8 Sep 1949.
COL Threlkeld rests forever in the Masonic Cemetery in Morganfield, Kentucky.