"Implacable" was ordered to join the Dardanelles campaign in March 1915, and she arrived shortly after the loss of "Irresistible". She supported the landings at Cape Helles and at Anzac Cove, the beginning of the land portion of the Gallipoli Campaign. On the day of the attack, 25 April, the ship steamed off X Beach at Cape Helles, bombarding Ottoman defences as men went ashore. In recognition of the critical support she had provided the troops as they attacked Ottoman positions, they named the landing site "Implacable Beach". She continued to support the ground forces into May, including during the First and Second Battles of Krithia. In May, she was reassigned to the 2nd Detached Squadron, which was tasked with supporting the Italian "Regia Marina" (Royal Navy) in the Adriatic Sea, where it contained the Austro-Hungarian Navy. In November, she was again transferred, this time to the 3rd Detached Squadron, based in Salonika, Greece. The ship was recalled to Britain in July 1917, later being converted into a depot ship for the Northern Patrol. "Implacable" was ultimately sold for scrap in 1921 and was broken up the following year in Germany.