In the first years of the 20th century, he served as Constructor of the Navy and Chief of the Bureau of Construction and Repair, with responsibility for naval shipbuilding.

Upon graduation, he served in the screw frigate Tennessee for the two years of sea duty then customary prior to receiving his officer's commission.

Later attached to the staff of Commodore George Dewey, commander of the Asiatic Squadron, Capps was present during the Battle of Manila Bay.

Among his notable innovations was the decision to mount battleships' main batteries on the centerline, thereby increasing their broadside weight of metal to the maximum.

Capps also served on a number of American and international committees which had been established for such purposes—among others—as improving the organization of the Navy and adopting new safety measures at sea to prevent a recurrence of disasters such as the sinking of the RMS Titanic in April 1912.

Although placed on the retired list effective 31 January 1928, Capps continued on active duty until the day of his death at Washington, D.C., on 31 May 1935.