In 1939, the impending Nazi invasion of Poland was an open secret. That August, representatives of Nazi Germany and the Soviet Union signed the Nazi-Soviet Pact, pledging mutual non-aggression for a period of two years.
Two days later, representatives of the United Kingdom signed the Agreement of Mutual Assistance with Poland, aligning Great Britain with the Franco-Polish Military Alliance. Should Poland be invaded by a foreign power, England and France were now committed to intervene.
The first fourteen “Unterseeboots” (U-boats) left their bases, fanning out across the North Atlantic. Hitler’s invasion of Poland, began, three weeks later. Even then, Hitler believed that war with England and France could still be avoided. The “Kriegsmarine” was under strict orders to follow the “Prize Regulations” of 1936.
England and France declared war on Nazi Germany on Septemebr 3. Hours later, U-30 Oberleutnant Fritz Julius Lemp fired a torpedo into the British liner SS Athenia. Lemp had mistakenly believed it to be an armed merchant vessel and fair game under Prize Regulations, but the damage was done. The longest and most complex naval battle in history, had begun.
As in WWI, both England and Germany were quick to implement blockades on one another. For good reason. By the time that WWII was in full swing, England alone would require over a million tons a week of imported goods, in order to continue the fight.
The “Battle of the Atlantic” lasted 5 years, 8 months and 5 days, ranging from the Irish Sea to the Gulf of Mexico, from the Caribbean to the Arctic Ocean. Winston Churchill would describe this as “the dominating factor all through the war. Never for a moment could we forget that everything happening elsewhere, on land, at sea or in the air depended ultimately on its outcome”.
Thousands of ships were involved in more than a hundred convoy battles, with over 1,000 single ship encounters unfolding across a theater thousands of miles wide. According to http://www.usmm.org, the United States Merchant Marine suffered the highest percentage of fatalities of any service branch, at 1 in 26 compared to one in 38, 44, 114 and 421 respectively, for the Marine Corps, Army, Navy and Coast Guard.
New weapons and tactics would shift the balance first in favor of one side, and then to the other. In the end over 3,500 merchant ships and 175 warships would be sunk to the bottom of the ocean, compared with the loss of 783 U-boats.
The most unusual confrontation of the war occurred on this day in 1945, in the form of a combat action between two submerged submarines. Submarines operate in 3-dimensional space, but their most effective weapon does not. The torpedo is a surface weapon, operating in two-dimensional space: left, right and forward. Firing at a submerged target requires that the torpedo be converted to neutral buoyancy, introducing near-insurmountable complexity into firing calculations.
The war was going badly for the Axis Powers in 1945, the allies enjoying near-uncontested supremacy over the world’s shipping lanes. At this time, any surface delivery between Nazi Germany and Imperial Japan was likely to be detected and stopped. The maiden voyage of the 287’, 1,799 ton German submarine U-864 departed on “Operation Caesar” on December 5, delivering Messerschmitt jet engine parts, V-2 missile guidance systems, and 65 tons of mercury to the Imperial Japanese war production industry.
The mission was a failure, U-864 having to retreat to the submarine pens in Bergen, Norway, for repairs after running aground in the Kiel Canal. The sub was able to clear the island of Fedje off the Norway coast undetected on February 6. By this time British MI6 had broken the German Enigma code. They were well aware of Operation Caesar.
The British submarine Venturer, commanded by 25-year-old Lieutenant Jimmy Launders, was dispatched from the Shetland Islands, to intercept and destroy U-864.
ASDIC, an early name for sonar, would have been far more helpful in locating U-864, but at a price. That familiar “ping” would have been heard by both sides, alerting the German commander that he was being hunted. Launders opted for hydrophones, a passive listening device which could alert him to external noises. Calculating his adversary’s direction, depth and speed was vastly more complicated without ASDIC, but the need for stealth won out.
Developing an engine noise which he feared might give him away, U-864’s commander, Ralf-Reimar Wolfram decided to return to Bergen for repairs. German submarines of the age were equipped with “snorkels”, heavy tubes which broke the surface, enabling diesel engines and crews to breathe while running submerged. Venturer was on batteries when the first sounds were detected, giving the British sub the stealth advantage but sharply limiting the time frame in which it could act.
A four dimensional firing solution accounting for time, distance, bearing and target depth was theoretically possible, but had rarely been attempted under combat conditions. Plus, there were unknown factors which could only be approximated.
A fast attack sub, Venturer only carried four torpedo tubes, far fewer than her much larger adversary. Launders calculated his firing solution, ordering all four tubes firing with a 17½ second delay between each pair.
With four incoming at as many depths, the German sub didn’t have time to react. Wolfram was only just retrieving his snorkel and converting to electric, when the #4 torpedo struck. U-864 imploded and sank, instantly killing all 73 aboard.
Surface actions were common enough between all manner of vessels, but a fully submerged submarine to submarine kill occurred only once in WWI, on October 18, 1914, when the German U-27 torpedoed and sank the British sub HMS E3 with the loss of all 28 aboard. To my knowledge, such an action occurred only this one time, in all of WWII.