"Torpedoes 1 and 2, set depth to 2 meters, gyro angle 0!"
When Zhang Hainuo issued this command, it was already 2:30 in the morning of the next day. U89 and U93 had arrived on time, while U122 had encountered a minor malfunction on the way, and both it and U145 would be about two hours late. Although this wolf pack of submarines only consisted of three vessels, considering that waiting for the other two submarines might miss the opportunity, Zhang Hainuo decided to launch the attack under the cover of darkness.
At this moment, including his U171, the three submarines had already positioned themselves for attack: U171 arrived first, taking advantage of its higher speed to flank the British convoy from the side, now positioned to the right front of the convoy. U89, the second to arrive, though Zhang Hainuo couldn't know the mood of its captain, diligently followed U171's instructions and lurked on the right side of the British convoy. Lastly, there was U93, a UD-class submarine similar to U89, originally designed for export but integrated into the German Navy's operational sequence after the outbreak of war. Under the command of Captain Rudolf, U93 quietly lurked on the left side of the British convoy.
This time, instead of ordering to retract the periscope and dive immediately after torpedo launch, Zhang Hainuo continued to observe the surface through the periscope. The white wakes left by the two T-type torpedoes quickly disappeared on the sea surface shrouded in darkness. Despite the strict lighting control on the British convoy, their massive hulls couldn't escape the keen eyes of the underwater hunters at this distance, especially with the thick black smoke billowing from their funnels.
Launching torpedoes at the midsection of the British convoy from this distance, Zhang Hainuo's primary objective was not to hit enemy vessels but to attract attention, enticing some of the escort warships to leave the convoy and create an opportunity for U89 and U93 to attack. However, if the torpedoes managed to hit enemy ships, it would create even greater chaos and add another accomplishment to his record. It would be hypocritical for Zhang Hainuo to say he didn't anticipate such an outcome.
There are two types of torpedo speeds in this era: one is low speed with long range, and the other is high speed with short range, which can usually be adjusted before torpedo launch. For German submarine commanders, as they often operate at close range, high-speed torpedoes are preferred for their superior effectiveness. Therefore, they typically set their torpedoes to a speed of over 40 knots. Of course, some may choose a speed of around 30 knots to reduce the wake generated by the torpedoes, as in the case of the torpedoes launched by U171 this time.
Forty seconds later, a massive explosion reverberated across the surface, followed by another explosion less than 5 seconds later.
The world before Zhang Hainuo suddenly brightened significantly. He saw two towering fireballs rising from the sea surface, illuminating the area for several nautical miles around them.
Zhang Hainuo was about to order to retract the periscope when he saw one of the fireballs expand exponentially in an instant! The newly formed fireball soared higher, seeming to reach the clouds, while its volume rapidly expanded with the increasing height, eventually resembling a mushroom cloud formed after an atomic bomb explosion in Zhang Hainuo's sight.
"We hit the jackpot this time!" Zhang Hainuo couldn't help but exclaim. He pulled his staff officer, Cook, beside him to the periscope. "Look, we hit an oil tanker!"
Before Cook could carefully look, Zhang Hainuo turned around and shouted to the other crew members, "We hit an oil tanker!"
Excited cheers erupted from the crew members, and at this moment, no one cared if they were on the edge of the battlefield!
"Lieutenant, that's a large oil tanker, at least 10,000 tons!" Cook said as he leaned in to observe the massive "fireworks" through the periscope.
"10,000 tons!" When Zhang Hainuo first saw the towering fireball, he only felt that it must be a tanker filled with oil, without considering how large it might be. Despite Cook's relatively low rank, he had served in the German Navy for four years, with experience on reconnaissance vessels and two submarines, making him quite knowledgeable.
The news of hitting the British oil tanker quickly spread from the control room to the other compartments. Cheers erupted one after another, indicating the unprecedented high morale among the crew. However, as the commander of this submarine, Zhang Hainuo quickly calmed down from his joy. He loudly announced:
"All right, everyone quiet down! The British destroyers are about to arrive. I now order the submarine to dive to a depth of 40 meters. Everyone, man your stations and prepare for shock resistance!"
Although it sounded somewhat illogical to change depth but not position after launching torpedoes, Zhang Hainuo had already figured it out. Since the British also thought so, and their sonar equipment could accurately detect submarines traveling underwater, why not refrain from running the engines and stay hidden in deep water, only to "play dead" if necessary? The chance of evading British attacks would be even higher. Moreover, U89 and U93 were nearby; as soon as they launched their attacks, the British destroyers coming to attack U171 would have to return to protect the merchant ships. By then, they would be forced to juggle their priorities, exhausting themselves.