As a young ensign, Pollock served aboard during the Spanish–American War. After the war, he rose through the ranks, served on several ships, and did important research into wireless communication. 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. Afterward, he was made the eighth Naval Governor of American Samoa and then the superintendent of the United States Naval Observatory, before retiring in 1927.