He served with the 3rd Engineers at Fort Leavenworth, Kansas, and subsequently served in the Philippines from 1909 to 1910. He later served in Mexico with General John J. Pershing, commanding the engineering company that built roads to allow supplies to be provided to the Army. He also served with Pershing in France during World War I. During World War I, he was placed in charge of the Intermediate Section and was responsible for building warehouses used to supply the Army in France. He received the Army Distinguished Service Medal for his efforts during the war, the citation for which reads:
The President of the United States of America, authorized by Act of Congress, July 9, 1918, takes pleasure in presenting the Army Distinguished Service Medal to Colonel (Corps of Engineers) Ernest Graves, United States Army, for exceptionally meritorious and distinguished services to the Government of the United States, in a duty of great responsibility during World War I. Colonel Graves was charged with the construction of the Grieves Storage Depot and later was appointed Engineer Officer of the Intermediate Section, Services of Supply, where he was placed in charge of all construction projects west of Bourges. As Engineer Officer of Base Section No. 2 and of the Advance Section, S.O.S., he performed the duties with which he was entrusted in a conspicuously meritorious manner. In the many responsible capacities in which he was employed the performance of his duty was characterized by sound judgment and untiring zeal.[2]
He was retired from the army in 1921 due to deafness.[3]