AT 12:30 P.M. SUNDAY, FINDING HIMSELF BRACKETED by patrol boats and destroyers, Schwieger ordered another fast dive. The line of vessels ahead seemed to be an antisubmarine cordon, with Fair Isle at the top and North Ronaldsay in the Orkneys at the bottom. Schwieger suspected the cordon might be a permanent presence in these waters. If so, he wrote in his log, by way of warning other captains, “it would not seem advisable to pass this line during the day, especially when visibility is very good.”
U-20 traveled submerged for the next four hours. At 4:30 P.M., Schwieger ascended to periscope depth and immediately spotted a patrol boat off to starboard. He dove back to cruising depth.
So much underwater travel was taxing for his crew. The atmosphere grew close and warm. But it was especially taxing for the submarine’s batteries. Even moving at a mere 5 knots, a boat of U-20’s class could cover a maximum of only 80 nautical miles before the batteries failed.
Schwieger kept the boat submerged for another two and a half hours. He noted in his log that his batteries were making a crackling noise. By this point U-20 had traveled 50 nautical miles on electric power.
At 7:00 P.M. Schwieger again tried his periscope and to his relief saw no imminent threat. “Emerged,” he wrote, “and steered towards the open sea in order to get away from the patrol boats whose smoke is still visible astern.”
In an addendum to his log, he noted that if still more destroyers had been posted beyond this Fair Isle–Ronaldsay line, thus forcing his boat to stay submerged even longer, “our situation could have been critical as our battery was pretty nearly gone.” These were deep waters—too deep for U-20 to hide on the bottom. Had the batteries failed here, Schwieger would have had no choice but to come to the surface and run until his diesel engines succeeded in recharging the system. But destroyers, capable of moving at speeds more than twice U-20’s maximum, would have had no difficulty overtaking him and would have begun firing long before.
Once safely out to sea and past the northern lip of Scotland, Schwieger set a course that would take him down the west flank of the Outer Hebrides, a bulwark of islands situated off Scotland’s northwest coast. His patrol zone off Liverpool was still a three-day voyage away.
The heave of the sea had lessened, producing swells of only 3 feet. Schwieger kept the boat on the surface. At 9:30 P.M. he signed his log to close the third day of his patrol.
Three days out, and he had sunk nothing—had not even fired his deck gun.
LATER THAT NIGHT, Schwieger was summoned into the shelter atop the conning tower. A lookout had spotted a potential target. In his log Schwieger described it as a “huge neutral steamer, its name lighted.” He judged it to be a Danish passenger liner out of Copenhagen, bound for Montreal. To determine this, Schwieger may have relied on his “War Pilot,” a merchant officer named Lanz, who served aboard U-20 to help identify ships. Between Lanz’s expertise and an immense book carried aboard every submarine that provided silhouettes and descriptions of nearly all ships afloat, Schwieger could be reasonably certain of the identities of any large vessel that came into view.
Though it’s clear Schwieger considered the Danish ship a potential target, he made no attempt to attack. The ship was too far ahead and moving too fast; he estimated its speed to be at least 12 knots. “An attack on this ship impossible,” he wrote in his log.
This entry revealed much about Schwieger. It showed that he would have been more than willing to attack if circumstances had been better, even though he recognized the ship was neutral—and not just neutral but heading away from Britain and thus unlikely to be carrying any contraband for Germany’s enemies. The entry revealed as well that he had no misgivings about torpedoing a liner full of civilians.