This isolation made the U-boat distinct among Germany’s naval forces. Surface ships usually traveled in groups and, given the height of their masts, could stay in contact with their bases; U-boats traveled solo and lost contact sooner, typically after sailing only a couple of hundred miles. Once at sea, a U-boat captain was free to conduct his patrol in whatever manner suited him, without supervision from above. He alone determined when and whether to attack, when to ascend or dive, and when to return to base. He had absolute control over the boat’s periscope. “I want to stress that the submarine is only a one-eyed vessel,” said a U-boat commander, Baron Edgar von Spiegel von und zu Peckelsheim, who knew Schwieger well. “That means, only the one who is at the periscope with one eye has the whole responsibility for attacking or the safety of his ship and crew.”
The view it provided was a crabbed one at best. A captain got only a brief, platelike glimpse at the world around him, during which he had to make decisions about a ship’s nature, its nationality, whether it was armed or not, and whether the markings it bore were legitimate or fake. And if he decided to attack, it was he alone who bore the responsibility, like pulling the trigger on a gun, but without having to see or listen to the result. All he heard was the sound of the exploding torpedo as transmitted through the sea. If he chose to watch the tragedy unfold, he saw only a silent world of fire and terror. Once, Spiegel attacked a transport carrying horses and watched one of the animals—“a splendid, dapple-gray horse with a long tail”—leap from the ship into an overloaded lifeboat. After that, he wrote, “I could not endure the spectacle any longer.” He pulled down his periscope and ordered his boat into a deep dive.
“It was a very hard task and entirely different from the fighting in the army,” said Spiegel. “If you were bombarded by artillery and you had orders to leave your trenches and attack you were in full excitement personally. In the submarine perhaps you were sitting in your small cabin drinking your morning coffee and [eating] ham and eggs when the whistle or the phone rang and told you, ‘ship in sight.’ ” The captain gave the order to fire. “And the results of these damn torpedoes were certainly very often heartbreaking.” One ship, struck in the bow, sank “like an airplane,” he said. “In two minutes the 10,000 ton ship disappeared from the surface.”
Such authority could be thrilling but carried with it a certain loneliness, amplified by the fact that Germany had very few submarines at sea at any one time. As of May 1915, Schwieger’s U-boat was one of only twenty-five in Germany’s fleet that were capable of traveling long distances. Only seven were in service at a time, owing to the fact that after each cruise the boats often needed several weeks for repair and overhaul. When on patrol, Schwieger’s U-boat occupied a pinpoint in a vast sea.
On this cruise, Schwieger carried with him a set of orders that had been delivered to him by hand. These were the result of a newly risen fear that Britain was about to launch an invasion of Germany itself, from the North Sea at Schleswig-Holstein, and that the ships carrying the invading troops would depart from ports different from those customarily used to resupply British forces in France. Intelligence reports had long suggested such an invasion might be in the works, but German naval officials were at first skeptical. Now, however, they had come to believe the reports might be true. Schwieger’s orders directed him to hunt and attack these transports in a designated square of sea off Liverpool, between England and Ireland, and to sail there “on the fastest possible route around Scotland.” Once there, the orders said, he was to hold that position “as long as supplies permit.”