Would some submarine warfare experts chime in on the Ken Burns flick?

I watched it last night and was generally impressed but one thing bothered me. He criticized cities on the East Coast for not turning their lights off at night and implied this contributed to the German submarines' success early in the war.

I thought submarines relied mostly on Sonar to find targets so what difference would it make if cities were blacked out? I know that some of their deadliest attacks took place miles from land where there was no light anyway.

It just seemed like a willful distortion of facts to make a point but I could be wrong.

I'd love for someone whose more knowledgeable than I am to clarify this.

At night they leaded the subs closer to the coastline with the lights on.
If they had blacked out,then the U-Boats would not have come in closer to shore.

Tankers hugged the coast, travelling from Venezuala and the Carribean up to New York and
New England.

Sonar is good for listening to ships, it really cant tell you where the shore is.


:hi:

Since America wasn't at war, the Kreigsmarine had little fear from sub-hunter warships, so U-boat crews would surface at night off large cities and ports and just watch and wait.

As a ship approached between themselves and the coast, they could make out the speed and course by the silhouette of the ships. Churchill implored the States to start enforcing blackouts for that very reason.

Successful sub operations at that time were still largely based on good intelligence, ie. knowing where a ship was going to be at such a time, patience, and good luck. If you can sit off the coast of a country along known shipping routes, it's pretty much a turkey shoot. That period was known as the "happy time" for German submariners; they had terrific success because the US didn't take the threat seriously.

Ships were sunk in waters so shallow, the superstructure would still be above the waterline when the keel hit bottom.

Besides, early in the war, U-boats had to sit on the surface at night to charge their batteries, anyway, so sonar would be useless. But if you are on the surface, a couple of miles offshore, city lights would silhouette ships passing by.

Modern sonar is amazing, but sonar as we now know it is a late-WW2/postwar development.

They fired off sounds waves that were reflected by the metal of the sub (or underseas mountains, whales, whatever).

AFAIK, subs didn't use sonar because it would have been a homing beacon for any destroyers listening for subs.

Subs did use listening equipment to detect engine noise. That and visual sighting were their primary tools.

Wikipedia claims sonar is either the 'active' kind I was referring to or 'passive', which would include listening for the engine noises, so subs did use sonar. Never mind.

Most of the time they would use the sonar, or radar for that matter with one
'blip' to get a range on the target, or destroyer.
Knowing that later in the war that Japan had radar on some ships, the subs didnt want to be
detected with using radar or sonar full time.
They would also us SD Radar as little as possible for aircraft detection, as some stations
would DF on their signal and send out anti-sub ops.

The U-boats of the Atlantic were far more rudimentary. The Germans tried to make radar detectors called METOX as a warning of radar on aircraft with limited success. Still, in the spring of 1942, the Atlantic and gulf coasts were pretty much smooth hunting for the U-boats.

By 1944, the only way for U-boats to evade aircraft was to stay submerged all the time. I suggest reading Herbert Werner's Iron Coffins for a vivid description of the operation of German submarines. (You've probably read it, but I make the suggestion for anyone else reading this.)

Yes more later in the war, they had SJ surface radar that was very good when it was working
that found alot of ships, if only the torpedoes were working before Admiral Lockwood came on
board at Pearl Harbor in September 1943.............:hi:

But they were a lot cheaper:

wow!

American subs tended to cruise on the surface and attack submerged. German U-boats, usually, but not always, cruised underwater and attacked on the surface.

Instead of shooting a fan of torpedoes from a safe distance hoping one would hit, Otto Kretchmer snuck in and surfaced where sonar could not detect his boat. He then cruised up and down the convoy choosing the most valuable targets and making the maximum effect of his limited ammuntion. A Type VII U-boat had five tubes. Once shot, the reload was slow. There were only about twelve torpedoes on board. Once spend, he submerged and drifted out of the convoy during the confusion. The conning tower of a U-boat is so small, that it is very hard to see at night.

Kretchmer himself was captured pretty early in the war and most of the handful of aces were killed pretty quickly when ASW improved.

:-)

Targeting was all done visually. America's second worse naval defeat ever was the shipping losses in the Atlantic by the Uboats. Peacetime lights were a major contributing factor. Dark-adapted eyes at sea easily saw the silhouettes of cargo ships against the bright cities. This made locating and targeting ships easy. Further, there were few escorts and no convoys in American waters. Merchants often successfully crossed the Atlantic under guard only to be shot to pieces of the U.S. coast. Spies in Europe and possibly here told the Kreigsmarine where ships were headed and the Uboats simply had to wait for them.

Adm. King decided at the beginning of U.S. direct involvement that the few U.S. escort vessels were to be used to guard troop ships rather than merchantmen. Sonar in WW II was mostly passive using hydrophones to locate the bearing of ship propellers. This was not accurate enough for aiming. That had to be done from the bridge or through the periscope. The Germans did not have active sonar until the very end of the war. The allies used it for locating dived U-boats. It was expensive and not in wide use until about 1943.

Most people are clueless about history.

with navigation. Simply put, before the advent of GPS and other systems like LORAN, submarines and other vessels still had to navigate using sextants. A sub would have to surface every so often to take sun or star shots. The bright lights of a New York or Boston would simplify this process. Head for the lights and wait in the near shore waters for a target to appear.

Also in regards to #8 and #11, yes U-boats did prefer to to surface and use their deck guns. A few shots with cheap and easily carried shells would sink most merchant ships. A small cramped U-Boat could carry many shells relative in proportion to the space taken up by torpedoes and their tubes. Torpedoes would be used more for large targets and armed ships.

It is pretty hard to miss a major seaport with the lights on.