When entering World War I, the U.S. Navy needed to protect American merchant ships from German submarine attack without diminishing the strength of the main battle fleet. This prompted the formation of a 55-ship patrol force made up entirely of older cruisers and destroyers, many of which were Spanish-American War veterans. Because she was the most iconic and best equipped, Olympia was immediately selected as the flagship of the fleet protecting the entire American Eastern seaboard.
With updated technology, including a sonar device, new weapons, and refitted radio system, Olympia was made ideal for patrols, convoy duty, and diplomatic opportunities. In 1918, as American troops joined their European Allies, Olympia was reassigned for Atlantic convoy service. Patrolling with merchant ships and troop transports, Olympia served as a shepherd watching over the ships in her care, ever ready to defend them from German U-boats as they made the perilous trip across the Atlantic.