In its simplest form the problem was to force a passage through the defended channel of the Dardanelles into the Sea of Marmora, to attack the capital of Turkey in Europe, to win through the Bosphorus into the Black Sea, securing each step in the advance against reconquest by the Turks, so that ships might pass from the Ægean to the Russian ports in the Black Sea, bringing to the Russians arms for their unequipped troops and taking from them the corn of the harvests of Southern Russia. The main problem was to force a passage through the defended channel of the Hellespont.
This passage had been forced in the past by a British naval squadron. In February, 1807, Sir John Duckworth sailed through with seven ships of the line and some smaller vessels, silenced the forts at Sestos and Abydos and destroyed some Turkish ships; and then, fearing that the Turks, helped by French engineers, would so improve the fortifications that he would never be able to get back, he returned. On his return, one of his ships, the Endymion frigate, 40 guns, received in her hull two stone shot each 26 inches in diameter.
The permanent fortifications guarding the Channel were added to and improved during the nineteenth century. At the outbreak of the war with Italy, four years ago, they were equipped (perhaps by German officers) with modern weapons. An attempt made by Italian torpedo boats to rush the Straits by night was discovered by searchlights and checked by a heavy fire from quick-firing and other guns. All the torpedo boats engaged in the operations were hit and compelled to return.
When Turkey entered the war against the Allied Powers, her officers had every reason to expect that the British or French fleets would attempt to force the Channel. The military prize, Constantinople and the control of the Black Sea (whether for peace or for offence), was too great a temptation to be resisted. Helped by their German allies they prepared for this attack with skill, knowledge and imagination. The Turks had no effective battle fleet, as in the sixteenth century, when they sought their enemies upon their own coasts; and had they had one they could not have passed the British fleet blockading the Dardanelles; but they prepared the channel and its shores so that no enemy ship might pass to seek them.
More than the two great wars, in South Africa and Manchuria, the present war has shown:
(a) that in modern war, defence is easier and less costly in men and munitions, however much less decisive, than attack;
(b) that the ancient type of permanent fortress, built of steel, concrete and heavy masonry is much less easy to defend against the fire of heavy modern howitzers and high explosives than temporary field works, dug into the earth and protected by earth and sandbags;
(c) that the fire of modern long range guns is wasteful and ineffective unless the object fired at can be accurately ranged, and the fire controlled by officers who can watch the bursting of the shells on or near the target;
(d) that in restricted waters the fixed or floating mine, filled with high explosive, is a sure defence against enemy ships.
Beginning with proposition (a), the Turks argued that (unlike most defences) a defence of the passage of the Dardanelles against naval attack might well be decisive (i.e., that it might well cause the attack to be abandoned or even destroy the attacking ships) since ships engaged in the attack would be under every disadvantage, since: