After the United States declared war on Germany on 6 April 1917 entering
World War I,
Ericsson was prepared for overseas duty.
Ericsson began patrol duty in the war zone, and almost at once came upon a surfaced U-boat shelling two sailing ships. She opened fire, forcing the submarine down and preventing further attack, then picked up 37 survivors of the sailing ships. She continued on patrol and escort duty, and on 28 September, at night, sighted a surfaced submarine, at which she fired.
Ericsson dropped
depth charges, but before she could carry out her plan to ram the German U-boat, she lost contact in the darkness.
Ericsson continued to sail out of Queenstown on patrol and escorting
convoys, many times attacking submarines, standing by damaged ships, and rescuing survivors. After June 1918, she was based at
Brest, France; and during that summer, usually sailed about ahead of convoys, towing aloft a
kite balloon used for observation. At the close of the war,
Ericsson was
overhauled at
Liverpool, but returned to Brest in time to take part on 13 December in the welcoming honors rendered for President
Woodrow Wilson, arriving in France on the transport . On 21 December,
Ericsson departed for the United States, arriving at New York on 8 January 1919. == Postwar ==