Schwieger sailed a southwesterly course. He saw no targets but also no threats and was able to stay on the surface the entire day. Toward nightfall, at 6:50 P.M., he at last spotted a potential target, a steamer of about two thousand tons. It flew a Danish flag off its stern, but Schwieger’s war pilot, Lanz, believed the flag was a ruse, that the ship was in fact a British vessel out of Edinburgh. It was heading toward U-20. Schwieger ordered a fast dive, to periscope depth.
Now began the complex choreography that would determine whether he could add this ship to his personal tally of sunk tonnage. Men ran back and forth under the direction of the ship’s chief engineer, to help keep the boat level, as the helmsmen adjusted the horizontal and vertical planes. Schwieger raised and lowered the periscope at brief intervals to keep the steamer in sight but minimize the amount of time the periscope and its wake were visible on the surface.
With his rangefinder, Schwieger gauged the ship’s distance and speed. Another indicator of velocity was the height to which water rose on the target’s bow. The higher and whiter, the faster. If this had been a French battleship, Schwieger would have had to watch especially closely, for the French navy painted false wakes on the bows of its warships, in an effort to confuse the calculations of U-boat commanders.
Schwieger had two kinds of torpedoes aboard—an old bronze model and the newest G6 torpedoes. The G6, or “gyro,” torpedo was bigger and more reliable, but Schwieger selected one of the bronze models, presumably in order to conserve the better torpedoes for more important targets, like the troop transports he would be hunting in Liverpool Bay. The crew armed it and flooded its launching tube, one of the two tubes in U-20’s bow. The boat had two others in its stern.
The men at the hydroplanes worked to keep the boat as steady and level as possible, lest the conning tower rise too high and betray the submarine’s presence, or the periscope sink below the surface and make aiming impossible.
The freighter approached, clearly unaware that U-20 was ahead. Schwieger positioned his boat at a right angle to the ship’s course and advanced slowly to maintain “steerage,” just enough forward motion to keep the hydroplanes and rudder engaged. The submarine was, in effect, a gun barrel and had to be pointed in the right direction at the time the torpedo was launched.
From the bow a crewman called, “Torpedo ready.”
TORPEDOES WERE weapons of great power—when they worked. Schwieger distrusted them, and with good reason. According to a German tally 60 percent of attempted torpedo firings resulted in failure. Torpedoes veered off course. They traveled too deep and passed under their targets. Their triggers broke; their warheads failed to explode.
Aiming them was an art. Through the restricted view afforded by the periscope, a captain had to estimate the forward speed of the target, its course, and its distance away. He aimed not at the target itself but at a point well ahead, as if shooting skeet.
Stories of torpedo mishaps were rife among crews. One U-boat experienced three torpedo failures in twenty-four hours. In the third of these, the torpedo turned unexpectedly and traveled in a circle back toward the boat, and nearly hit it. Another submarine, UB-109, of a class used primarily for coastal patrols, tried launching an attack while surfaced. The first torpedo, fired from its stern, left the tube and immediately sank. The captain maneuvered the boat so that he could take another shot, this time from the bow. But, according to a British intelligence report, “This torpedo broke surface 5 or 6 times, described a complete circle, and also missed the target.”
Torpedoes were expensive, and heavy. Each cost up to $5,000—over $100,000 today—and weighed over three thousand pounds, twice the weight of a Ford Model T. Schwieger’s boat had room only for seven, two of which were to be held in reserve for the homeward voyage.
If the performance measured by the German navy were to hold true for Schwieger on this patrol, it would mean that if he fired all seven of his torpedoes, only three would succeed in striking a ship and exploding.
SCHWIEGER’S TARGET—the presumed British ship, flying Danish colors—continued its approach. It was 300 meters away, the U-boat equivalent of point-blank range, when Schwieger gave the order to fire. The command was repeated throughout the boat.
What should have come next was a whoosh and a tremor as the torpedo left its tube, followed by a sudden, perceptible rise of the bow due to the lost weight, this immediately suppressed by the men at the hydroplanes.
But Schwieger heard nothing and felt nothing. There was only silence.
The torpedo never left the tube. A misfire—a locking mechanism had failed to release.
The target continued on its way into the safe, deep waters of the North Atlantic, its crew apparently unaware of how close they had come to disaster.
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