In February 1917, as a result of the German resumption of unrestricted submarine warfare, and the resulting heavy shipping losses in the Western Approaches, Rosemary, together with the rest of the 10th Sloop Flotilla, was transferred to Queenstown (now Cobh) in the South of Ireland, to be deployed on escort duties. By July that year, Rosemary had transferred to the Northern division of the Coast of Ireland Station, with headquarters at Buncrana. On 6 August 1917, Rosemary was part of the escort for Convoy HH.11, bound from Newport News to Glasgow and west-northwest of Tory Island when the merchant ship was torpedoed and sunk by the German submarine . None of the escort spotted the submarine. On 12 December 1917, Rosemary was in collision with the destroyer , with Wolverine sinking as a result. Two of Wolverines crew were killed.
