"Ocean" transferred to the Dardanelles in late February 1915 to participate in the Dardanelles campaign. On 28 February, she took part in an attempt to suppress the Ottoman defences in the Dardanelles led by Admiral John de Robeck; the battleships "Albion" and led the operation, and were tasked with neutralizing the repaired fortress at Dardanus, while "Ocean" and supported them by engaging batteries of mobile field guns that had proved to be troublesome in previous attempts to neutralise the Ottoman defences. "Ocean" initially attempted to locate guns that had been active in the vicinity of Sedd el Bahr, before moving on with "Majestic" and coming under fire from several Ottoman batteries, including howitzers around Erenköy. The British battleships eventually silenced the guns, but only temporarily; as soon as the ships moved on to other targets, the guns opened fire again. In the meantime, "Albion" and "Triumph" had approached Dardanus but they came under heavy fire from Ottoman guns on the European side of the straits, including the fortress at Erenköy, and were forced to circle to avoid taking hits. Unable to engage Dardanus under these conditions, the ships instead opened fire on the guns at Erenköy, which initially seemed to be effective, as the Ottoman fire slackened. "Ocean" and "Majestic" approached in an attempt to attack Dardanus, but they too came under renewed, furious fire from Erenköy, and de Robeck again ordered a withdrawal. The only success came after the four battleships withdrew from the straits and a landing party from "Triumph" went ashore and disabled several light guns. The inability of the British and French fleets to neutralize the mobile field guns convinced the Allied command that the only way forward would be to make a major amphibious assault to clear the guns by land.