He held major posts ashore and afloat, chief of which were commanding the naval forces intervening in Haiti (1915–16) and Santo Domingo (1916), and Commander-in-Chief, Pacific Fleet, from July 28, 1916, to April 30, 1919.

Completing the course of instruction in October of that year, he became Inspector of the 15th Light House District at St. Louis, Missouri, and served in that capacity until April 15, 1907.

He thereafter became Secretary of the Light House Board, Department of Commerce and Labor, on October 11, 1909, and served in that assignment until June 30, 1910, when he was ordered to duty in attendance upon the summer conference of officers at the Naval War College, Newport, Rhode Island.

Relieved of command of Cruiser Force, Atlantic Fleet, he returned to the United States, reporting to Key West, Florida.

Upon designation as Commander in Chief, Pacific Fleet, by the President of the United States on July 22, 1916, he proceeded to San Diego, California, to assume his new duties in the rank of admiral, and hoisted his flag in USS Pittsburgh.

He was in charge of the patrol of the East Coast of South America which cleared southern waters of German raiders during World War I and he greatly aided in the development of goodwill between the United States and her Allies.

For his services as Commander in Chief of the Pacific Fleet during World War I, he was awarded the Distinguished Service Medal with citation as follows: For exceptionally meritorious service in a duty of great responsibility as Commander-in-Chief of the Pacific Fleet on the East Coast of South America in establishing friendly diplomatic relations with the countries of South America.On November 1, 1918, ten days before the signing of the Armistice which officially closed hostilities between Germany and the United States, Admiral Caperton was designated by the President of the United States as Special Representative with the rank of Ambassador Extraordinary and Plenipotentiary to attend the ceremonies at Rio de Janeiro on November 15, 1918, incident to the inauguration of Francisco de Paula Rodrigues Alves as President of the Republic of Brazil.

On his flagship, USS Pittsburgh, Admiral Caperton made courtesy visits to South American republics during the war and since the Armistice was signed.

His visits were of inestimable value, as they strengthened the bonds of friendship between South American republics and the United States and promoted solidarity of relations between these countries and the Allies.