Unrestricted Submarine Warfare

Sinking of an enemy armed troopship steamer by German submarine in the Mediterranean Sea.
by Willy Stöwer

Early submarines were rather fragile beasts. They had two sources of propulsion: diesel engines for running on the surface, and electric motors for running submerged. The electric motors were run off of battery power. Running at speed underwater would quickly drain the batteries which would force the submarine to surface and use its diesel engines to recharge the batteries. Something best done at night when the submarine, due to its not having much of a superstructure, was harder to spot.

Early submarines had two types of armament: torpedoes and one or more guns mounted on the deck of the submarine. Obviously the guns couldn't be used while submerged whereas the torpedoes could be used either surfaced or submerged. As torpedoes were generally rather large items, a submarine couldn't carry many of them so, in the early days of World War I, a submarine captain's preferred method of attack was to surface and use the submarine's deck gun(s) on the target.

If you think about it, it seems clear that surfacing to bang away at a target with a gun isn't a very good idea against a warship, they typically have more (and bigger) guns than a submarine. Generally submarines were used as commerce raiders, sinking the ships supplying an enemy nation, not the enemy's warships. (Though in World War II, Japanese doctrine expected submarines to attack warships, not merchant ships.)

According to the old rules, submarines were required by international law to stop merchant ships, check their papers to see if they were carrying "contraband" or war material, then, if the ship was carrying something which would allow the submarine to sink it, the submarine had to make provisions for the crew to be "removed to safety," and guess what, taking to the lifeboats didn't count.

So submarine captains, in order to stay alive, started bending the rules. So lifeboats were considered, by the sub captains, "removed to safety." No doubt the merchant crews disagreed when they were hundreds of miles from shore!

So let's say you're an island nation, like the United Kingdom, and you're getting rather tired of German submarines sinking your ships. Not always playing by the rules either, mind you. Now there's a couple of things you can do if you're concerned about this sort of thing: 1) have your merchant ships sail in convoys, escorted by warships, while this won't prevent a submarine attack, it will force them to stay submerged, or 2) arm your merchant ships with guns of their own, so they can blast away at any submarine precocious enough to surface and demand that you stop.

Now if you're a submarine owner, odds are you will no longer surface to attack a merchant ship. Odds are you will simply put a torpedo into the ship and, as is said, "let God sort them out." Now as submarines back in the day were generally slower than a merchant ship while traveling submerged, you'd want to lie in wait where enemy ships were likely to appear. Subs would travel on the surface at night (where they could travel rather fast, even faster than most merchant ships) to position themselves for an attack.

At night they could use torpedoes or guns to attack the often unarmed merchant ships, then dive to avoid the escorts before they could fire back at the sub. Necessity, being the mother of invention, is why the Allies invented (during WWI) what the British called ASDIC* but which we impertinent Yanks called (and still call) sonar (actually SONAR is more correct**), a device used to detect offending submarines in order to drop explosives on them, causing them to sink.

Now under the old rules, submarines were restricted in what they could do as regards attacking shipping. They had to obey the rules, what was considered "restricted submarine warfare." As the folks who were getting their ships sunk by submarines came up with new ways to stop that, the best way being to sink the enemy submarines, merchant ships began to be armed. The British went one better, they would take older merchant ships and hide guns on them, the unsuspecting German U-Boat commanders would sail up, demand they heave to and...

Yup, hidden guns come out, submarine gets blown out of the water.

Eventually word gets out and the Germans start sinking anything flying an Allied flag. Without regard to any rules, what is called "unrestricted submarine warfare." Generally ships which looked like (and actually were) passenger liners were left alone. Until the Allies started using them to carry troops and war material that is.

Passenger liners were designed to be very fast, after all, the faster they were, the faster they could travel across the ocean, deposit their paying customers, then pick up more paying customers. So they were actually (in general) faster than a submarine, even running on the surface. So the U-Boats would lie in wait for them, near where they sailed from, or where they were sailing to...

Which is how the Lusitania was sunk by a German U-Boat. She was getting close to her destination when a torpedo sent her to the bottom. Killing a number of civilians (including a hundred plus Americans) but also sending a quantity of war material to the bottom as well. Technically, Lusitania was a valid target. Not one of the British Admirality's finer moments.

RMS Laconia was a former passenger liner converted to a troopship in World War II. On the 12th of September, 1942, she was torpedoed off the coast of West Africa by the German U-156 under the command of Korvettenkapitän Werner Hartenstein.

Laconia had some 2,732 crew, passengers, soldiers, and Italian prisoners of war on board...

Operating partly under the dictates of the old prize rules, the U-boat commander, Korvettenkapitän Werner Hartenstein, immediately commenced rescue operations. U-156 broadcast their position on open radio channels to all Allied powers nearby, and were joined by the crews of several other U-boats in the vicinity.

After surfacing and picking up survivors, who were accommodated on the foredeck, U-156 headed on the surface under Red Cross banners to rendezvous with Vichy French ships and transfer the survivors. En route, the U-boat was spotted by a B-24 Liberator bomber of the US Army Air Forces. The aircrew, having reported the U-boat's location, intentions, and the presence of survivors, were then ordered to attack the sub. The B-24 killed dozens of Laconia's survivors with bombs and strafing attacks, forcing U-156 to cast their remaining survivors into the sea and crash dive to avoid being destroyed.

Rescue operations were continued by other vessels. Another U-boat, U-506, was also attacked by US aircraft and forced to dive. A total of 1,113 survivors were rescued; however, 1,619 were killed – mostly Italian POWs. The event changed the general attitude of Germany's naval personnel towards rescuing stranded Allied seamen. The commanders of the Kriegsmarine were shortly issued the Laconia Order by Grand Admiral Karl Dönitz, which specifically forbade any such attempt and ushered in unrestricted submarine warfare for the remainder of the war. (Source)

Much has been made (by some) of the "war crime" committed by the crew of the B-24 and the officer who ordered them to attack the submarine. The ability of an aircrew, during peace or wartime, to spot banners and light communications from a small ship on the surface are very limited. They may (or may not) have noticed any sign from the rescuers that they were indeed rescuing people from the Laconia.

German admiral Dönitz issued another order regarding the rescuing of people from a sunken ship, War Order No. 154. At Nuremberg, this (and the Laconia Order) were introduced into testimony in order to convict Dönitz of war crimes.

The United States had also practised unrestricted submarine warfare, under their own equivalent to the Laconia Order, which had been in force since they entered the war. Fleet Admiral Chester Nimitz, the wartime commander-in-chief of the US Pacific Fleet, provided unapologetic written testimony on Dönitz's behalf at his trial that the US Navy had waged unrestricted submarine warfare in the Pacific from the very first day the United States entered the war.

The prosecution has introduced much evidence surrounding two orders of Dönitz, War Order No. 154, issued in 1939, and the so-called Laconia Order of 1942. The defence argues that these orders and the evidence supporting them do not show such a policy and introduced much evidence to the contrary. The Tribunal is of the opinion that the evidence does not establish with the certainty required that Dönitz deliberately ordered the killing of shipwrecked survivors. The orders were undoubtedly ambiguous and deserve the strongest censure.

The evidence further shows that the rescue provisions were not carried out and that the defendant ordered that they should not be carried out. The argument of the defence is that the security of the submarine is, as the first rule of the sea, paramount to rescue and that the development of aircraft made rescue impossible. This may be so, but the [Second London Naval Treaty] is explicit. If the commander cannot rescue, then under its terms he cannot sink a merchant vessel and should allow it to pass harmless before his periscope. The orders, then, prove Dönitz is guilty of a violation of the Protocol.

In view of all the facts proved and in particular of an order of the British Admiralty announced on 8 May 1940, according to which all vessels should be sunk on sight in the Skagerrak, and the answers to interrogatories by Admiral Chester Nimitz stating unrestricted submarine warfare was carried on in the Pacific Ocean by the United States from the first day of the Pacific War, the sentence of Dönitz is not assessed on the ground of his breaches of the international law of submarine warfare. (Source)

I thought this was an interesting story. It's hard to enforce rules upon combatants during wartime. But afterwards, make sure your own guys are innocent before going after the losers of the war.

War is messy, things aren't always clear cut.

U-156 (foreground) and U-507 pick up Laconia survivors on 15 September, three days after the attack.

Yup, war sucks.





* ASDIC = Anti-Submarine Detection Investigation Committee, the group of British, French and American scientists who developed early sonar devices.
** SONAR is an acronym standing for SOund NAvigation and Ranging. In common use though it's usually rendered as "sonar."