A glance at the map will show that the Marmora was not only distant from the British naval base, but that the only line of approach was of an uncommonly formidable character. The channel of the Dardanelles is narrow and winding, with a strong tide perpetually racing down it, and setting strongly into its many bays. It was, moreover, protected by forts with powerful guns and searchlights and torpedo tubes, and by barrages of thick wire and netting; it was also patrolled constantly by armed ships. Yet all these defences were evaded or broken through with marvellous courage and ingenuity; for nearly a year a succession of brilliant commanders took their boats regularly up and down the passage, and made the transport of Turkish troops and munitions first hazardous and finally impracticable. Two battleships, a destroyer, and five gunboats fell to them, besides over thirty steamers, many of which were armed, nine transports, seven ammunition and store ships, and no less than 188 sailing ships and dhows with supplies. It is hardly necessary to add that in no case was violence done to neutrals or non-combatants. The first officer to take a British submarine up the Dardanelles was Lieutenant Norman Holbrook. It was in December 1914 that his attempt was made, and after equipping his boat, B11, with ingenious devices for jumping obstacles, and running several preliminary trials, he trimmed and dived for Sedd-el-Bahr at the moment when the searchlights were extinguished at dawn. Rather more than four hours after his start he had passed the Straits and was at last able to put his periscope above water. He found his fortune at the same moment. There, on his starboard beam, was a large two-funnelled vessel, painted grey, and flying the Turkish ensign. At 600 yards he fired his starboard torpedo, and dipped for a few seconds. An explosion was heard. B11 came quietly to observation depth again of her own motion, and her commander, still at his periscope, saw the grey ship firing a number of guns. His boat dipped again, but he got her up once more, and this time saw his enemy, the battleship _Messudiyeh_, silent, and sinking slowly by the stern. He turned for home, dived into the channel, and ran along the bottom at full speed; came up to take his bearings, dived again, and by 2 p.m. had cleared the exit. In ten hours he had proved all the possibilities of a novel campaign. He had forced the strongly-barred channel, surprised and sunk a battleship in broad daylight, and returned to report, though he had gone up without information and come down with a damaged compass. Of the boats which followed in the spring and summer of 1915, the most famous were E14 (Lieutenant-Commander E. Courtney Boyle); E11 (Lieutenant-Commander M. E. Nasmith); E12 (Lieutenant-Commander K. M. Bruce); E7 (Lieutenant-Commander Cochrane); E2 (Commander David Stocks); and K1 (Lieutenant Wilfred Pirie). In efficiency all these surpassed