On 17 February 1915, a British seaplane from HMS Ark Royal flew a reconnaissance sortie over the Straits.^{[2 ]}Two days later, the first attack on the Dardanelles began when an Anglo-French flotilla, including the British dreadnought HMS Queen Elizabeth, began a long-range bombardment of Ottoman coastal artillery batteries. The British had intended to use eight aircraft from Ark Royal to spot for the bombardment but all but one of these, a Short Type 136, were unserviceable.^[3] A period of bad weather slowed the initial phase but by 25 February the outer forts had been reduced and the entrance cleared of mines.^[4] Royal Marines were landed to destroy guns at Kum Kale and Seddülbahir, while the naval bombardment shifted to batteries between Kum Kale and Kephez.^[4]

Frustrated by the mobility of the Ottoman batteries, which evaded the Allied bombardments and threatened the minesweepers sent to clear the Straits, Churchill began pressuring the naval commander, Admiral Sackville Carden, to increase the fleet's efforts.^[5] Carden drew up fresh plans and on 4 March sent a cable to Churchill, stating that the fleet could expect to arrive in Istanbul within 14 days.^[6] A sense of impending victory was heightened by the interception of a German wireless message that revealed the Ottoman Dardanelles forts were running out of ammunition.^[6] When the message was relayed to Carden, it was agreed the main attack would be launched on or around 17 March. Carden, suffering from stress, was placed on the sick list by the medical officer and command was taken over by Admiral John de Robeck.^[7]

18 March 1915

On the morning of 18 March 1915, the Allied fleet, comprising 18 battleships with an array of cruisers and destroyers, began the main attack against the narrowest point of the Dardanelles, where the straits are 1 mi (1.6 km) wide. Despite some damage to the Allied ships by Ottoman return fire, minesweepers were ordered along the straits. In the Ottoman official account, by 2:00 p.m. "all telephone wires were cut, all communications with the forts were interrupted, some of the guns had been knocked out ... in consequence the artillery fire of the defence had slackened considerably".^[8] The French battleship Bouvet struck a mine, causing her to capsize in two minutes, with just 75 survivors out of 718 men.^[9] Minesweepers, manned by civilians, retreated under Ottoman artillery fire, leaving the minefields largely intact. HMS Irresistible and HMS Inflexible struck mines and Irresistible was sunk, with most of her surviving crew rescued; Inflexible was badly damaged and withdrawn. There was confusion during the battle about the cause of the damage; some participants blaming torpedoes. HMS Ocean was sent to rescue Irresistible but was disabled by a shell, struck a mine and was evacuated, eventually sinking.^[10]

The French battleships Suffren and Gaulois sailed through a new line of mines placed secretly by the Ottoman minelayer Nusret ten days before and were also damaged.^[11] The losses forced de Robeck to sound the "general recall" to protect what remained of his force.^[12] During the planning of the campaign, naval losses had been anticipated and mainly obsolete battleships, unfit to face the German fleet, had been sent. Some of the senior naval officers like the commander of Queen Elizabeth, Commodore Roger Keyes, felt that they had come close to victory, believing that the Ottoman guns had almost run out of ammunition but the views of de Robeck, the First Sea Lord Jackie Fisher and others prevailed. Allied attempts to force the straits using naval power were terminated, due to the losses and bad weather.^[12] Planning to capture the Turkish defences by land, to open the way for the ships, began. Two Allied submarines tried to traverse the Dardanelles but were lost to mines and the strong currents.^[13]