The Dardanellesis a 61km (28 mile) strait between Europe and Asiatic Turkey. The maximum width is 7km and in the area known as the Narrows, the distance is no more than 1,600 metres. The Dardanelles Straits are overlooked by high cliffs on the Gallipoli Peninsula.
On the outbreak of the First World War, the Dardanelles Straits were under the control of Turkey. They were protected by outer fortresses on either shore at Kum Kale and Sedd el Bahr, linked by a run of shore batteries and minefields to the fortresses at Chanak and Kilid Bahr.
On 26th December 1914, Britain's War Council discussed the possibility of attacking Turkey in order to re-open the Dardanelles Straits. It was argued that if the operation was successful it would encourage some of the neutral Balkan states to join the Allies.
Admiral Carden proposed a three-stage operation: the bombardment of the Turkish forts protecting the Dardanelles, the clearing of the minefields and then the invasion fleet travelling up the Straits, through the Sea of Marmara to Constantinople. Carden argued that to be successful the operation would need 12 battleships, 3 battle-cruisers, 3 light cruisers, 16 destroyers, six submarines, 4 sea-planes and 12 minesweepers. Lord Kitchener, the War Minister and Winston Churchill, the First Lord of the Admiralty, liked the plan, and on their advice, Herbert Asquith, the Prime Minister, agreed for operation to go ahead.
It was hoped that the navy would force a way through the Dardanelles on its own. However, it was decided to send British troops and units of the Australian and New Zealand Corps (ANZAC) led by General William Birdwood to the Greek island of Lemnos in case they were needed to take part in the operation.
On 19th February, 1915, Admiral Carden began his attack on the Dardanelles forts. The assault started with a long range bombardment followed by heavy fire at closer range. As a result of the bombardment the outer forts were abandoned by the Turks. The minesweepers were brought forward and managed to penetrate six miles inside the straits and clear the area of mines.
Further advance up into the straits was now impossible. The Turkish forts were too far away to be silenced by the Allied ships. The minesweepers were sent forward to clear the next section but they were forced to retreat when they came under heavy fire from the Turkish batteries.
Winston Churchill became impatient about the slow progress that Carden was making and demanded to know when the third stage of the plan was to begin. Admiral Carden found the strain of making this decision extremely stressful and began to have difficulty sleeping. On 15th March, Carden's doctor reported that the commander was on the verge of a nervous breakdown. Carden was sent home and replaced by Vice-Admiral de Robeck, who immediately ordered the Allied fleet to advance up the Dardanelles Straits.
On 18th March eighteen battleships entered the straits. The fleet included Queen Elizabeth, Lord Nelson, Agamemmon, Inflexible, Ocean, Irresistible, Prince George and Majestic from Britain and the Gaulois, Bouvet and Suffren from France. At first they made good progress until the Bouvet struck a mine, heeled over, capsized and disappeared in a cloud of smoke. Soon afterwards two more ships, Irresistible and Ocean hit mines. Most of the men in these two ships were rescued but by the time the Allied fleet retreated, over 700 men had been killed. Overall, three ships had been sunk and three more had been severely damaged.