British blockade of the coast of Asia Minor

At noon on 2 June 1915 a British naval blockade of the coast of Asia Minor on the Aegean Sea came into force. That same morning the Foreign Office notified the governments of the neutral states. In a note to the United States ambassador in London, preserved in the American diplomatic papers, the Foreign Secretary, Sir Edward Grey, defined the blockaded area by latitude: from 37°35′ to 40°05′ north, including the entrance to the Dardanelles. It therefore covered the whole Turkish coast from the mouth of the strait roughly to the latitude of the island of Samos, together with Smyrna. Neutral ships were given 72 hours to leave the blockaded area.

Submarines in the Aegean

The immediate cause of the decision was the appearance off the Dardanelles of the German submarine U-21. At the end of May, within three days, she sank the battleships Triumph and Majestic. Admiral John de Robeck had to withdraw most of his heavy ships to the safe harbour of Mudros, and the British feared that more submarines would follow U-21. The indented coast of Asia Minor, with countless bays and channels between the islands, seemed an ideal place for their secret supply bases. Destroyers and smaller vessels searched it systematically, but this demanded an enormous effort from an already overstretched fleet.

How tense the situation was had been shown by a recent incident at Bodrum, a port long suspected of supplying submarines. According to the British official history, the French cruiser Dupleix found it full of vessels and announced that they would be searched. When, after talks with the local governor, she sent boats into the harbour under a white flag, the Turks opened fire on them, inflicting serious casualties. Dupleix shelled the town, and on 28 May the British cruiser Bacchante with the destroyer Kennet destroyed all the vessels in the harbour as well as the castle and barracks. Such ad hoc operations were, however, judged insufficient. On de Robeck’s initiative it was decided to place the whole mainland coast from the Dardanelles to Samos under formal blockade. No such steps could be taken against the islands, which did not belong to Turkey.

How the blockade was run

A formal blockade allowed the stopping and seizure of any ship bound for the blockaded coast, even under a neutral flag. The base of the blockade became the Gulf of Gera on the island of Lesbos, called Port Iero by the British. The officer in command was stationed there in a battleship or cruiser, and with the consent of the Greek authorities an airfield was also set up there. The British official history notes that the Greek inhabitants of the island were friendly to the British. In the following weeks the British entrusted the Smyrna area, from the Gulf of Edremit to the island of Chios, to the so-called Smyrna patrol. It usually consisted of two large ships, two destroyers, an armed boarding steamer, two trawlers with indicator nets for detecting submarines and a minesweeper adapted for minelaying. Further south, as far as Samos, the blockade was maintained by a French patrol. On 6 June the government in Paris announced that the French navy would maintain the blockade on an equal footing with the British.

The British hoped the blockade would deepen the food shortages in Constantinople reported in more and more intelligence. The main aim, however, was naval: to prevent German submarines from finding fuel, supplies and hiding places in the Aegean. The blockade complemented the operations of British submarines, which at the same time were paralysing Turkish shipping in the Sea of Marmara. At the end of August the French extended it to the rest of the coast of Asia Minor and Syria, from Samos to the border of Egypt.