Battle for Atlantic (later stages)

[Chris Allen]

My main question is what happened after May 1943?

I understand that Doonitz's main aim was to sink allied ships faster
than they could be re-built. This would force Britain out of the war.

This did not work so well before this date because

1) Enigma intercepts allowed Britain to direct convoys away from places
places where they knew U Boats were gathering. Consequently U-Boats did
not find as many ships as he had hoped.

2) Allied capcity to find and sink U-Boats steadily improved so he had
fewer effctive U-Boats that he wanted.

3) Allied ship building improved more than he had thought likely.
Combined with the pints above, this meant allies had more ships than
before, rather than fewer.

Despite these set backs for Doonitz, some people in Britain believed
they could not "hang in there", even as late as Feb/March 43.

Then starting in May 43 it all came together for the allies.
Now they had enough air cover to "close the gap".
More to the point, allied ships & aircraft were fitted with better
systems to hunt & kill U-Boats.
Doonitz now lost U-Boats much faster than he could replace them so he
called off the campaign.

So what happened in the Atliantic after this point?

How many allied ships were attacked by U-boats?
Were allied ships regarded as "safe"?
Were convoys still used to the end of the war?

I'm guessing the allies had to at least pretend to fear the U-Boats and
continue with convoys. To do otherwise would effectively tell Germany
"We can read your signals".

[Les]

On Thursday, May 26, 2016 at 10:22:43 AM UTC-3, Chris Allen wrote:

(stuff deleted)

Post by Chris Allen
So what happened in the Atliantic after this point?

Doenitz realized the "Wolf Pack" tactics could no longer
work, because the Allies could trace U-boat transmissions
and attack spotter U-boats before the pack could form.

His first response was to equip his U-boats with more AAA,
and instruct them to "fight it out" with the Allied
aircraft that usually spotted them. It didn't end well.

Subsequently, he stopped requiring his U-boats to give
regular transmissions, and let them sail solo missions
and attack targets of opportunity. This effectively
allowed Allied convoys to move with little to no
casualties.

Post by Chris Allen
How many allied ships were attacked by U-boats?
Were allied ships regarded as "safe"?

No, but the convoys became safer.

Post by Chris Allen
Were convoys still used to the end of the war?

Yes, because they were the safest means for shipping.

(rest of post deleted)

[Geoffrey Sinclair]

Post by Chris Allen
My main question is what happened after May 1943?
I understand that Doonitz's main aim was to sink allied ships faster than
they could be re-built. This would force Britain out of the war.
This did not work so well before this date because
1) Enigma intercepts allowed Britain to direct convoys away from places
places where they knew U Boats were gathering. Consequently U-Boats did
not find as many ships as he had hoped.

Actually post May 1943 the U-boat numbers in the Atlantic declined
so there was little need for evasive routing. Evasion was a major
tactic in the second half of 1941. Later convoys had more escorts
as well as support groups that could be added to the escort if required.

Post by Chris Allen
2) Allied capcity to find and sink U-Boats steadily improved so he had
fewer effctive U-Boats that he wanted.

The allies found more U-boats and their attacks were more deadly
on average that earlier in the war.

The U-boat fleet grew from 73 at the end of December 1940, to 236
at the end of December 1941, to 381 end December 1942, to 424
end December 1943. Essentially the 240 U-boat losses in 1943
were still less than the gains. However the front line boat numbers
were declining, that is those available after taking away the training
boats and the ones working up.

Front line boats, end of year, 1939 was 34, 1940 was 27, 1941 was 88,
1942 was 204, 1943 was 159.

The numbers of U-boats deployed for use in the Atlantic and North Sea
peaked at 207 in May 1943 (out of 240 front line boats) and was down to
122 in December. So essentially the Germans ran down the U-boat fleet
deployed against the Atlantic convoys.

Post by Chris Allen
3) Allied ship building improved more than he had thought likely.
Combined with the pints above, this meant allies had more ships than
before, rather than fewer.

The big losses in 1942 took until 1943 to replace.

Post by Chris Allen
Despite these set backs for Doonitz, some people in Britain believed they
could not "hang in there", even as late as Feb/March 43.

The early 1943 battles were a major concern because convoys with
good escorts were taking heavy losses, if convoying failed what was
left to do? The British were worried but not as worried as you imply.

Post by Chris Allen
Then starting in May 43 it all came together for the allies.
Now they had enough air cover to "close the gap".

Long range B-24 and escort carriers. Plus support groups
that could be allocated to convoys under threat or simply
hunt U-boats without having to cover merchant ships.

Post by Chris Allen
More to the point, allied ships & aircraft were fitted with better systems
to hunt & kill U-Boats.

As well the invasion of North Africa had pulled in a lot of anti
submarine assets, which were largely released for the Atlantic
battles in the first half of 1943, plus the extra escorts and aircraft
being built.

Post by Chris Allen
Doonitz now lost U-Boats much faster than he could replace them so he
called off the campaign.

He called off the campaign in the North Atlantic routes.

In August, with more flak guns on the U-boats, better radar detectors
and acoustic torpedoes they tried again, by October they had been
defeated again and tried small groups of 2 or 3 boats.

Also in October 1943 the allies began using the airfields in the Azores.

Post by Chris Allen
So what happened in the Atliantic after this point?

The allied shipping movements went up, the number of attacks
declined.

Axis submarines in all theatres sank about twice as many merchant
ships in the first 5 months of 1943 as they did in the remaining 7
months. In fact the sinkings in the first 5 months of 1943 of 314
ships, 1,782,768 GRT comes close to the tonnage sunk by axis
submarines for the rest of the war.

Post by Chris Allen
How many allied ships were attacked by U-boats?

If you want attacks you would need to compile this from German
records as it needs to include the misses.

Rohwer's Axis Submarine Successes is the best published work.

The RN official history says 31 ships of 175,013 GRT were lost
in the Atlantic and Arctic in 1944, another 19 ships of 122,729
GRT in 1945, this can be compared to the 1939 losses, 47 ships
of 249,195 GRT.

Post by Chris Allen
Were allied ships regarded as "safe"?

Safer, not absolutely safe.

Post by Chris Allen
Were convoys still used to the end of the war?

Yes, even post war, in case there were some fanatics.

Post by Chris Allen
I'm guessing the allies had to at least pretend to fear the U-Boats and
continue with convoys. To do otherwise would effectively tell Germany "We
can read your signals".

Allow the allies to note it was easier to hunt U-boats if the
merchant ships were mostly in convoy, rather than sailing
individually.

The allies noted the demise of the wolf packs, that still left U-boats
on lone patrols, which had to be guarded against. As 1944 went on
they began to allow more sailings out of convoy, mainly because
they were still short of shipping.

In 1944/45 the U-boats increased their operations around the
British Isles, after declining to 25 ships lost in 1943 to all causes
in these waters the merchant shipping losses were 77 ships
277,905 GRT in 1944 and 73 ships 233,331 GRT in 1945.

U-boat operations were done in the Indian Ocean as well.

The last convoy battle was off Kola Inlet with British, Canadian
and Soviet ships clearing a path for convoy RA.66, on 29 April
1944 of the 14 U-boats present 2 were sunk along with one escort.

The last U-boat sunk by allied surface combatants was on
6 May 1945, by air attack on 8 May.

Geoffrey Sinclair
Remove the nb for email.

[Rich Rostrom]

Post by Chris Allen
My main question is what happened after May 1943?
So what happened in the Atlantic after this point?
How many allied ships were attacked by U-boats?
Were allied ships regarded as "safe"?
Were convoys still used to the end of the war?

Month/Ships lost/Tonnage/U-Boats sunk

8/43 25 119,801 25
9/43 29 156,419 9
10/43 29 139,861 26
11/43 29 144,391 19
12/43 31 168,524 8
1/44 26 130,635 15
2/44 23 116,855 20
3/44 25 157,960 25
4/44 13 82,372 21
5/44 5 27,297 23
6/44 26 104,084 25
7/44 17 78,756 23
8/44 23 118,304 34
9/44 8 44,805 23
10/44 4 11,668 12
11/44 9 37,980 8
12/44 26 134,913 12
1/45 18 82,897 12
2/45 26 95,316 22
3/45 27 111,204 34
4/45 22 104,512 57
5/45 4 17,198 28

Total 445 2,185,782 481

(Data from the appendix to _U-505_ by RAdm Dan Gallery.)

Note that during this late stage, the Allies lost
over 400 ships of over 2M tons. The Germans lost
even more U-boats, but the seas were far far from
safe for Allied ships.

Post by Chris Allen
I'm guessing the allies had to at least pretend to fear the U-Boats and
continue with convoys. To do otherwise would effectively tell Germany
"We can read your signals".

The Allies had to continue with convoys and fear
the U-boats because the U-boats were still dangerous.

ULTRA did not provide every U-boat's position every
day; there were always gaps in the intercepts, and
there were always some U-boats operating at discretion.

With the number of U-boats at sea, protected convoys
remained necessary.

There _was_ one point when there might have been a
risk of disclosing ULTRA. IIRC the U.S. used ULTRA
to pick off all the German auxiliary ships at sea
to supply U-boats. Getting _all_ of them was thought
to look suspicious.

[Rich Rostrom]

Post by Rich Rostrom
ULTRA did not provide every U-boat's position every
day; there were always gaps in the intercepts, and
there were always some U-boats operating at discretion.

There was also at least one case of a U-Boat commander
getting his orders mixed up, and going to a position
many km from where he was ordered to be.

The Allies had read his orders and redirected a convoy
to avoid the position given there. But the altered
route took the convoy right over where the U-Boat had
actually gone by error.

This of course led to the convoy's being sighted
and reported to U-Boat HQ, and a subsequent
wolfpack attack on it.

[WJHopwood]

On Saturday, May 28, 2016 at 1:10:04 PM UTC-4,
Rich Rostrom wrote:
.......

There _was_one point when there might have
been a risk of disclosing ULTRA. IIRC the U.S.
used ULTRA to pick off all the German auxiliary
ships at sea to supply U-boats. Getting _all_ of
them was thought to look suspicious.

Just to clarify the term, "ULTRA" did not define
only one specific signals intercept system.
ULTRA was not comparable to the U.S
code-breaking term called MAGIC, which, if
its very existence had become compromised
it would have been a serious security breach.
ULTRA was a term established by the British
as a "catch-all" cover-name for a number of
methods and sources used by the Allies in their
signals intelligence activities. It is well-defined
in the book, "Codebreakers-The Inside Story of
Bletchley Park," (1993) as follows:
"ULTRA-British cover-name from June
1941, for all high-grade signals intelligence,
derived not only from "Enigma" but from "Fish"
and hand-ciphers, and from Italian and
Japanese codes and ciphers; later adopted
with some variants by the U.S."

WJH

[SolomonW]

Post by Chris Allen
Doonitz now lost U-Boats much faster than he could replace them so he
called off the campaign.

Doonitz plan B was that the Uboat campaign even after 1943, was costing the
Allies more than the Germans, even if the Uboats were not sinking that many
merchants ship.

[David Wilma]

Do the U-boat losses include losses due to mines? I imagine most mines in shipping lanes would be set by U-boats.

[Geoffrey Sinclair]

Post by David Wilma
Do the U-boat losses include losses due to mines? I imagine
most mines in shipping lanes would be set by U-boats.

While U-boats did lay mines it was mostly early in the war, the
majority of the mining done by Germany used surface ships
and aircraft.

Allied merchant ships lost to mines according to the RN, in all areas, were

78 ships, 262,542 GRT in 1939
201 ships, 509,889 GRT in 1940
111 ships, 230,842 GRT in 1941
51 ships, 104,488 GRT in 1942
37 ships, 108,658 GRT in 1943
28 ships, 95,855 GRT in 1944
28 ships, 93,633 GRT in 1945

(Think mining of the approaches to Antwerp as well as UK waters
in 1944/45).

This amounts to 6.5% of the merchant shipping tonnage loss and
10.3% of ships lost, indicating many victims were smaller coasters.
Or to put it another way the average U-boat victim was around 5,200
GRT, the average mine victim was around 2,600 GRT, the average
victim of S-boats was 2,300 GRT.

Geoffrey Sinclair
Remove the nb for email.

[Don Phillipson]

Post by David Wilma
Do the U-boat losses include losses due to mines? I imagine most
mines in shipping lanes would be set by U-boats.

The question probably concerns U-boats sunk (by all means),
not ships sunk by U-boats.

The RAF laid many more British sea mines 1939-45 than did
all vessels of the RN. Luftwaffe bombers also laid many mines.