 Returning from winter maneuvers off Cuba in March 1917 , the ship was in the York River when the United States declared war on Germany on 6 April , entering World War I. After fitting out at Brooklyn Navy Yard , she got underway from New York on 15 May with Cummings , Nicholson , Cushing , and Sampson , and joined convoy at Halifax , Nova Scotia , en route to Ireland . Upon arrival at Queenstown on 24 May , O 'Brien was assigned to the 6th Destroyer Division which cooperated with the British forces . She patrolled off the Irish coast in company with other destroyers answering distress calls and meeting eastbound convoys to escort them through the war zone . 
