In the morning half a gale was blowing, and although the submarine scare was still at its height de Robeck felt that the Navy could not leave the Army entirely in the lurch. The Majestic was ordered back to Helles again, and she remained off-shore all through that day and the following night. A half-cynical fatalism prevailed on board; in the officers’ wardroom the last of the champagne and the port was drunk on the grounds that it would have been a pity to see it go to the bottom.

At 6.40 the following morning the cry ‘Torpedo coming’ went up, and the sailors ran for the boats. The strike was made so low down on the port side there was scarcely a tremor on deck, but immediately afterwards a loud explosion shook the ship and she heeled over to port. The crew were given just fifteen minutes to get off before she sank bottom upward, her bows resting on a sandbank by the shore and exposing a fraction of her keel above the surface. A moment before the end a sailor ran the full length of the keel with the sea closing in around him. He reached the exposed bows just in time, and sat astride there until presently a boat came by and took him off. Forty-eight of his shipmates were lost. For the rest of the campaign the upturned hulk of the battleship remained there, like some stranded whale washed up on the shore.

For a few minutes it looked as though they were going to catch the U 21. Air Commodore Samson was circling overhead, and he dropped his bombs on the U-boat through the clear water. But Hersing dived under the French battleship Henri IV, and when Samson picked him up again, steaming up the Dardanelles in the sunshine, all his bombs were gone. But he permitted himself a gesture: he swooped and emptied his rifle on to her hull. The U 21 was last seen moving into the Narrows, and at some point in the Sea of Marmara must have passed Nasmith returning from Constantinople.

Thus on this one day, May 25, almost in one hour, two submarines, the German U 21 and the British E 11, brought an entirely new element into the campaign, and it was almost as important as the twenty Turkish mines which had been sown so fortuitously in Eren Keui Bay when the Allied Fleet attacked in March.

Nasmith’s raid was, perhaps, the more telling of the two, for it caused the Turks to issue an immediate order that for the time being no further reinforcements were to be sent to the peninsula by sea. Instead of a short overnight voyage the soldiers were now faced with a roundabout train journey of 150 miles to Uzun Keupri on the Adrianople line. Thence a single road led down into the peninsula, another hundred miles away — a march of at least five days for the men, and of considerably more for the bullock carts and the camels that were now obliged to bring in their equipment. Other supplies had to be sent down the Sea of Marmara by small boats which hugged the coast and travelled only by night. All this meant a drastic slowing down of Liman’s line of supply. ‘Had the British managed to increase their undersea offensive,’ he says in the study of the campaign which he wrote after the war, ‘the Fifth Army would have starved.’ And the German naval historian adds: ‘The activity of the hostile submarines was a constant and heavy anxiety, and if communication by sea had been completely severed the Army would have been faced with catastrophe.’ At one point the Turks on the peninsula were down to 160 rounds of ammunition per man.

Liman is a little tart about the activities — or rather the lack of activity — of the German Navy. The story was spread in Germany, he says, that the Goeben and the German submarines carried the main burden of the defence at Gallipoli; but the Goeben never took part at all, and the U 21, having got safely through to Constantinople and been much fêted there, emerged only once again. She came out of the straits on July 4 and sank the French transport Carthage. Finding that his return route was blocked, Hersing turned west and steamed for the Adriatic, to be seen no more. Yet he had achieved his purpose. The mere threat of his presence off Gallipoli had scattered the Allied battle fleet, and his two sinkings were enough to keep it in harbour in the islands ever afterwards.

For the British submarines, however, the situation was rather more difficult; in order to make good the work that had already been done by Boyle and Nasmith they had to keep up the pressure in the Sea of Marmara and if possible increase it; and indeed, in all the records of the Royal Navy there is hardly anything that quite compares with the undersea offensive that now began. In a world that has since grown used to the unearthly courage of young men with fantastic machines it is still difficult to credit some of the things that happened. Six-pounder guns were fitted to the decks of the submarines to help them eke out their supply of torpedoes, and two new arrivals, the E 12 and the E 7, ran up to Constantinople, where they bombarded the powder mills, put a torpedo into the arsenal, cut the railway line and chased the trains along the shore. Soon the commanders learned to handle the changing density of the water, and they even turned it to advantage; by lying on top of the layer of heavier specific gravity when they wished to hide or rest they saved themselves the danger and difficulty of diving great depths to the ocean floor.

It was on Boyle’s third trip into the Marmara, on July 21, that a new hazard was discovered. As he passed through the Narrows he saw an obstruction under the water, and he reported this to Lieut.-Commander Cochrane in the E 7, when he met her in the Marmara next day. On July 24 Cochrane came out and he confirmed Boyle’s report: the Germans were building a net. He himself had been entangled in it for half an hour, ninety feet down.

This was a much more formidable obstacle than anything the submarines had encountered before. By the end of July it was completed — a vast steel mesh of two-and-a-half-inch wire stretching entirely across the straits, and reaching 220 feet down to the floor of the channel. A line of buoys painted alternately red and black supported it on the surface, and one end was secured on the peninsula about a mile north of Maidos, the other on a steamer anchored near Abydos on the Asiatic side. Turkish motorboats loaded with bombs patrolled the surface like spiders waiting at the edge of a web. Specially sited guns were set up on either bank.

There was a gate in the middle of the net, and unless the submarines were lucky enough to strike it their only way of getting through the wire was to ram it at full speed underwater and hope for the best. Boyle described this experience: ‘I missed the gate and hit the net. I was brought up from eighty feet to forty-five feet in three seconds, but luckily only thrown fifteen degrees off my course. There was a tremendous noise, scraping, banging, tearing and rumbling, and it sounded as if there were two distinct obstructions, as the noise nearly ceased and then came on again, and we were appreciably checked twice. It took about twenty seconds to get through.’

But Cochrane on his next trip did not get through. Hopelessly entangled, he fought the net for twelve hours on the bottom of the straits while bombs exploded about him, and it was only when the hull was leaking and the lights had failed that he burned his papers and rose to the surface to surrender.

Nasmith, Boyle and the others were not deterred; they continued to pass through, and by the end of the year the net was so damaged by their repeated rammings it had almost vanished altogether. Up to the last, however, the passage through the Narrows remained an ordeal of the most frightening kind, and perhaps from that very fact it acted as a psychological stimulus on the crews. One seems to have read the story in some boyhood book of sea adventure: the pirates’ cave with its treasure lies hidden in the cliffs, but one has to make a dangerous dive beneath the sea to reach it. And some get through and some get trapped halfway.