In September 1939, "New York" joined the Neutrality Patrol, safeguarding sea lanes in the North Atlantic, and served as flagship with the Atlantic Squadron, later redesignated the United States Atlantic Fleet, for the next 27 months. In July 1941, she protected a convoy of U.S. troops moving to garrison Iceland. She was in the midst of a refit on 7 December 1941, when the Imperial Japanese Navy attacked Pearl Harbor, sinking many of the battleships in the U.S. Pacific Fleet and bringing the United States into World War II.