Sims enlisted in the Army on April 2, 1929, months before the beginning of the Great Depression.  He married his wife Dorothy, who was ten years younger than Harold.  They settled in Lincoln, Nebraska and had two children - Harley in 1937 and Marilyn in 1939.  During those years, Sims worked as a professor and assistant ROTC instructor.  In 1940 and throughout WWII, he served at the University of Nebraska as part of the Detached Enlisted Men's List Cadre.  Detached enlistedmen, later branded 'unassigned branch,' was a catch-all branch for men with such unique and specialized skills that did not fall into the other specific branches within the Army.  Sims became a part of the Army Specialized Training Program (ASTP), tailored for men and officers with great technical skills.  In October 1949, after 20 years of service as an enlistedman, he was promoted to the rank of Chief Warrant Officer.

On June 21, 1950, after training with mortars and artillery at Camp Carson, he was assigned to Headquarters Company, 2d Battalion, 29th Infantry Regiment, stationed on Okinawa.  The 29th remained on Okinawa for the first few weeks of the war, until receiving orders to mobilize two battalions (the 1st and 3d) for combat on July 14th. All three battalions were dramatically understrength and hardly prepared for movement.  The 2nd Battalion was stripped of men in a frantic effort to bring the other two battalions up to strength, and Sims was transferred to the  3d Battalion HQ Company.  "[When] the U.S.S. General Walker docked at Naha Port, every warm body coming down the gang plank immediately became infantry, field gear and weapons were issued, and men were assigned to various companies. We still were not at TO&E strength...We departed for Sasabo Japan supposedly for six weeks of preparatory training.  Daylight found us at anchor with Sasabo Japan shoreline in sight and Japanese sampans along side loading coal for our boilers. At that time we were told that orders had been changed. We were to proceed directly to Pusan where we would have three just days to get organized."

The men of the 29th Infantry arrived in Pusan on July 24th, and were on the move to Chinju the next day.  These two battalions from the 29th Infantry would be the only U.S. units blocking enemy attacks toward Pusan from the west.  With poor training and little to no intelligence, the 29th Infantry was hardly prepared for combat.   "Upon arrival in Pusan, we were informed that we would not have three days to prepare and organize, as the 24th Division, to which the 29th In RCT was attached, needed help immediately. The RCT loaded on a train and deployed to Chinju. At Chinju the Regt made an effort to get organized, but at about midnight the 3rd Bn was dispatched to Haedong.  In the meantime, 8th Army had totally lost track of the 4th and 6th NKPA Divisions.  On 25 July the 3rd Bn came into contact with the 6th NKPA Division after a violent four hour battle, the 3rd Bn was virtually annihilated. Out of over 900 men initially deployed with the 3rd Bn, sources [report] only about 158-228 men present for duty, many of them walking wounded. The Bn had in excess of 300 men killed, and some say 200 captured with many later massacred. When the 3rd Bn tangled with the 6th Division at Haedong, despite their terrible losses, they disrupted the NKPA plan to sneak in and take Pusan from the rear while the NKPA forces still had the initiative"."

A few days later, the straggling 3d battalion received word "that the 19th Inf was under heavy attack. The 3rd Bn was to attack through them to relieve pressure then continue on and retake the town of Chinju. Those of us that were there on 3 Aug 50 then found ourselves in what history now tells us was the Battle of the Notch. We had the entire 4th NKPA Div by the tail. After a day long battle, at times hand to hand, plus being strafed by our own Air Force P51 fighter planes, the north Koreans had enough and broke off the fight."

The 1st Battalion, 29th Infantry was then attached to the 35th Infantry Regiment, 25th Divsion on August 2nd.  It was later renamed 3d Battalion, 35th Infantry, and Sims paperwork shows that on September 4th, he was assigned to Headquarters Company.  In May 1951, Sims received the Bronze Star medal for his meritorious service from July 24 through November 2, 1950.  His citation notes that through the "most adverse combat conditions, he evinced great resourcefulness and a thorough knowledge of administrative procedures...and contributed materially to the effectiveness of his unit in combat."

Considering the harrowing conditions in the first few months of the war, the unpreparedness and inexperience of the men of the 29th Infantry, it is clear that CWO Sims' award is well deserved. Despite his usual duties as an administrator with HQ Co., there is no doubt that he participated directly in the intense combat of the end of July and August.  Between engaging in close combat and maintaining unit records and paperwork, Sims' performance in Korea is quite admirable, especially for a man quite a bit older than the rest of the troops.  By 1950 he was already 42 years old!

A year after he arrived in Korea, CWO Sims returned to the United States.  For three years, he was stationed at Fort Riley with the 10th Quartermaster Company and then with the 85th Infantry Regiment.  On November 1, 1954, he was assigned to Headquarters and Headquarters Detatchment, 66th Counter Intelligence Corps (CIC) Group, U.S. Army Europe (USAREUR) and remained with them until September 8, 1955 when he returned to the States.  Finally, after serving in the Army for 26 years, CWO Sims received an honorable discharge and retired from the service.