Chapter 191 Scapa Flow

Wilhelm originally intended to emulate the surprise attack on Pearl Harbor for Scapa Flow Naval Base. However, the navy's surface fleet proved uncooperative, leaving the task to submarines. Fortunately, he had prepared for this on two fronts, collaborating with Dönitz for the raid plan and conducting specialized training for years.

To be precise, it was a threefold preparation. If the submarine attack failed, he planned to launch an aerial assault with the air force and naval aviation. However, such an approach would likely result in significant losses to the air fleet, and the effectiveness of the bombing was uncertain.

Finally, just a week ago, U-47 submarine, loaded with secret weapons, departed from Kiel Harbor.

Following a meticulously planned route via Wilhelmshaven to the North Sea, the U-47 altered its course southward to submerge and avoid detection by surface vessels. They operated submerged during the day and surfaced at night.

With the sky now completely dark, U-47, having spent an entire day underwater, surfaced, adjusting its course. Sailors took advantage of the opportunity to climb onto the deck for a brief breath of fresh air. The sea breeze, briny and cool, hit their faces as a mist hung over the water, accompanied by the rhythmic sounds of waves.

Even in the North Atlantic at night, the sea was far from calm. The submarine swayed with the waves, a reminder that, at this stage, it was not a submersible but rather a vessel capable of submerging. Submarines under 1000 tons couldn't match the seafaring capabilities of larger warships. At least for now, submarines were vessels that could dive underwater, not yet fully submerged.

"What beautiful weather." Prien muttered softly, cigarette in hand, gazing at the bright stars in the sky. They were close to Scapa Flow, and this surface break was the final one in this mission. The remaining journey would be completed underwater, navigating through dangerous waters.

Of course, it could also be their last time on the surface.

Running his greasy hands through his hair, Prien dismissed such ominous thoughts. Days of continuous sailing had left him with a full beard, and his hair was quite oily, as if a squeeze could yield a few drops of oil. Freshwater was particularly precious on long voyages; the water tap was strictly managed, and submariners were allocated a tea kettle's worth of water for daily personal hygiene, including face washing and tooth brushing. They often used a damp towel after brushing their teeth for a quick face wash. So, the luxury of shaving, washing hair, or bathing was out of the question.

The brief break concluded, sailors, one after another, crawled back inside the submarine. Prien, after one last glance around to ensure no issues, was the last to slip inside. "Dive to a depth of 30 meters, maintain course. Turn off the main lighting power in 5 minutes."

After over seven hours of continued navigation, the submarine finally arrived at the entrance to the Pentland Firth around 1 AM the next day. "Attention, everyone! We face the risk of being sunk every minute from now on! Be ready for battle!"

According to previous intelligence, infiltrating Scapa Flow through the Pentland Firth route was extremely difficult, nearly impossible. To prevent submarine attacks, the strait, less than a kilometer wide, was filled with deliberately sunken ships and other underwater obstacles.

However, due to this very reason, the defenses here were relatively lax. Therefore, Dönitz chose this route, and U-47 was proceeding along it.

The term "extremely difficult" wasn't an exaggeration. A powerful tidal current flowed into Scapa Flow from here. U-47, caught in this tidal stream, seemed like a canoe in a raging river, swaying unpredictably. The submarine not only had to contend with the current but also avoid collisions with underwater obstacles. The most dangerous moment was when everyone onboard heard the sound of the submarine hull colliding with the underwater cables laid on the seabed. This collision nearly ran the submarine aground, and if Prien hadn't ordered an emergency surfacing by emptying the ballast tanks in time, they might have met their end there.

In this precarious situation, as if walking on a razor's edge and experiencing several life-and-death moments, they finally entered Scapa Flow.

"God bless us!" Prien let out a long sigh of relief, wiping the sweat from his face.

"Perhaps our ancestors' spirits are blessing us." The chief mate, panting heavily, replied while holding onto a nearby railing.

Prien nodded. "It's time to avenge them." Saying this, he walked to the periscope to observe the situation outside.

"Heh, impressive!" Prien couldn't help but exclaim. What he saw was an immensely massive fleet. Although it was late at night and he couldn't discern the specific types of warships, just by looking at the colossal silhouettes, it was evident that these were ships of at least twenty to thirty thousand tons.

He immediately gave an excited order. "Prepare for action!"

When he said "prepare for action", it didn't mean preparing to launch torpedoes. This time, they were preparing to use a different weapon: the secret weapon, "human-guided torpedoes."

Speaking of "human-guided torpedoes", the most famous example would be a certain island nation's "Kaiten" human-guided torpedoes.

These "Kaiten" torpedoes were modified from Type 93 oxygen torpedoes, with a diameter of one meter. The torpedo's interior could accommodate one crew member, who used a small periscope to locate the enemy ship and control the torpedo. The explosive payload carried by "Kaiten" was 1.36 tons, three times that of a standard torpedo.

In November of the 44th year, the first batch of "Kaiten" was transported by submarine mothership to the operational area, ready to attack the US fleet. Unexpectedly, the anti-submarine capabilities of the US forces were formidable. Before the "Kaiten" could be released, the torpedo motherships were hit and exploded. Only a few managed to approach the American ships, but under the intense gunfire of the US warships, only one US oil tanker was sunk at anchor.

However, it is less known that the development of human-guided torpedoes began with the Italians, and they had successfully developed and deployed them by the end of World War I, sinking the flagship of the Austro-Hungarian Navy, the "Viribus Unitis." Unfortunately, for the Austro-Hungarian Empire, which surrendered to the Allies just three days later, the attack had no practical significance.

These Italians were quite persistent and continued to develop their human-guided torpedoes. In 1935, they designed a large-sized human-guided torpedo known as the "Slow Torpedo", later becoming more famous as the "Pig" (Maiale). It earned this name because of its appearance resembling a swimming pig and its ease of manipulation. Two crew members could straddle the torpedo body. The "Pig" was powered by a 1.1 horsepower electric motor, with 30 60-volt batteries installed between the crew members and at the rear. It could travel 4 miles at 4.5 knots or 15 miles at 2.3 knots.

German engineers improved this torpedo, increasing its length by 0.5 meters to a total of 7.8 meters. The original 1.8-meter length with a 300-kilogram tactical bomb head was enhanced to 2 meters with a 350-kilogram tactical bomb head in the German version. The battery capacity was also significantly improved.

This time, they brought four of these torpedoes, or more accurately, propellers. These four propellers were fixed on the outer shell of the submarine on both sides. Later, they would have to climb out of the submarine, detach these four propellers, fix the tactical bomb head launched from the torpedo tube onto the propellers, approach the enemy ship, detach and secure the tactical bomb head to the ship's bottom, set a timed explosion, and finally retreat using the remaining propellers.