In 1917, less than a week before the United States entered World War I, he won a race against a fellow officer to receive the U.S. Virgin Islands from Denmark, and served as the territory's first acting governor.

During the war, he was promoted to captain and a vessel under his command transported 60,000 American soldiers to France, for which he was awarded a Navy Cross.

As Governor of American Samoa, Pollock is notable for establishing dialogue with the Mau movement, which eventually led to the dissolution of opposition groups.

[6] He remained in China for two and a half years as part of the Asiatic Squadron, then transferring to USS Detroit before returning home in 1897.

[12] After a brief leave, Pollock was assigned to the USS Chesapeake (as the watch and division officer), a position he held for more than one year.

[21] In the final days before the entrance of the United States into World War I, the U.S. military was concerned that Germany was planning to purchase or seize the Danish West Indies for use as a submarine or zeppelin base.

[23] Although the United States was not yet at war with Germany, the U.S. signed a treaty to purchase the territory from Denmark for 25 million dollars on March 28, 1917.

[24] The United States announced plans to build a naval base in the territory to aid in the protection of the Panama Canal.

During the war, Pollock was appointed as captain on USS George Washington, a German cruise liner which was seized by the United States government for use as a military transport ship.

[27] In 1918, George Washington was tasked to deliver President Woodrow Wilson to the Paris Peace Conference, though Pollock would not make the trip.

[32] At this time, American Samoa was administered by a team of twelve officers and a governor, with a total population of approximately 8,000 people.

[33] Beginning in 1920, a Mau movement, from the Samoan word for "opposition", was forming in American Samoa in protest of several Naval government policies, some of which had been implemented by Terhune but which were not revoked following his death, which natives (and some non-natives) found heavy-handed.

In addition, the United States Navy also prohibited an assembly of Samoan chiefs, whom the movement considered the real government of the territory.

Ripley, who had traveled to Washington to meet with Secretary of the Navy Edwin C. Denby, was not permitted by Evans to enter the port at American Samoa and returned to exile in California, where he later became the mayor of Richmond.

Although Ripley maintained that American "occupation" of Samoa was usurpation, he agreed to allow Pollock to govern unfettered and to provide him with copies of his letters.

Almost immediately after arriving on the island, Pollock and Secretary of Native Affairs S. D. Hall met with representatives of the Mau, becoming the first governor to do so.

The "wild man," clad only in nature’s vestments, was seen descending a coconut tree and was subdued by the Samoan, who bound his hands and brought him to the Naval Station.

The "wild man," who appeared to be quite elderly with nearly white hair, was physically frail but seemed content and at peace in his new surroundings, where he was well treated.

Before long, Samoan residents recognized the so-called “wild man” as Malua, the fourth and final runaway survivor from the Solomon Islands.

[37] Immediately on leaving Samoa, Pollock was appointed superintendent of the United States Naval Observatory in Washington, D.C., replacing outgoing Rear Admiral William D.

[40] On January 24, 1925, Pollock commanded the dirigible USS Los Angeles on a flight from Lakehurst, New Jersey, to photograph a solar eclipse from an altitude of 8,000 feet (2,400 m).

[42] In 1930, Pollock and his wife purchased a summer home in Jamestown, Rhode Island, while continuing to maintain their main residence in Washington, D.C.