Major General Hamlet was commissioned an Infantry Officer upon graduation from Infantry Officer Candidate School on July 11, 1944.

He served with the 366th Infantry Regiment and the 370th Infantry Regiment, 92nd Division in Italy during World War II. After the war, he qualified first as a liaison pilot and later graduated from Army Aviation School and qualified as a helicopter pilot in 1951.

He held a variety of command and staff positions before being assigned to Fort Leavenworth in the Army Combat Developments Command Combined Arms Agency from August 1963 to May 1966. Major General Hamlet then served a tour of duty in the Republic of Vietnam. First as the Operations Officer for the 11th Aviation Group, 1st Cavalry Division, and then Commander of the 227th Aviation Battalion.

His subsequent assignments were from February 1968 to June 1969 as Chief, Air Mobility Branch, Doctrine and Systems Division, United States Army Combat Developments Command Combat Arms Group, Fort Leavenworth, Kansas; August 1969 to June 1970  Student, United States Army War College, Carlisle Barracks, Pennsylvania;  July 1970 to June 1971 Commander, 11th Aviation Group, 1st Cavalry Division (Airmobile), Vietnam; June 1971 to December 1971 Assistant Division Commander, 101st Airborne Division (Airmobile), Vietnam; December 1971 to August 1972 Commanding General, 3rd Brigade, 1st Cavalry Division, Vietnam; and August 1972 to December 1974 Commanding General, 4th Infantry Division (Mechanized) and Fort Carson, Colorado.

From December 1974 to September 1977, he served as Deputy Inspector General, (Inspections, Safety, and Survey), United States Army, Washington D.C. While serving as the Deputy Inspector General he was extended on active duty by the Secretary of the Army until his retirement in 1981 with over thirty-seven years of active service.

Major General Hamlet’s military awards include the Distinguished Service Medal, the Legion of Merit (with three Oak Leaf Clusters), the Distinguished Flying Cross, the Soldiers Medal, the Bronze Star (with two Oak Leaf Clusters), and the Combat Infantryman Badge (2nd Award).