Battle for Atlantic

[Chris Allen]

My main question is what happened after May 1943?

I understand that Dooitz's main aim was to sinks 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 "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 fitter 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".

[Don Phillipson]

Post by Chris Allen
My main question is what happened after May 1943?
. . . 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".

Separate aspects include:
1. The role of aircraft in ASW and the "air gap" in the
Atlantic Ocean ( out of range of land-based patrol
aircraft 1939-42.) The gap was later filled by long-range
aircraft (Liberator and Catalina) and "escort carrier" ships.
2. British maintenance of the BAMS merchant ship cipher years
after the Kriegsmarine had cracked it.
3. Enigma decipherment (which failed when the U-boat
service added an extra rotor.)
4. ASW tactical methods (for air patrol as well as
escort ships) vis-a-vis U-boat methods (patrol lines,
wolf packs, surface attacks by night.)
5. Naval hardware, especially the "Hedgehog" mortar
(RN) and the Schnorkel (KM.)
6. Changing policy on convoys (especially the late
USN adoption of convoys in 1942.)

[William Clodius]

<snip>
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 fitter 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?

As long as the Allies continued to take the threat seriously, they had
the situation under control. Losses remained significant untill the end
of the war, so the allies always took it seriously. As a result Allied
losses rmained much less than the rate of replacement. German losses
remained higher than a country with reasonable alternatives would have
accepted. Their losses in almost all other efforts were so large, and
the resources involve sufficiently small, that until the end it was felt
that continuing the U-boat effort was more useful than stopping. The
loss rate to U-boat crews was very large, but the loss rates for an
infantry rifleman and bomber crew was not a lot lower and there were
many more of them. A loss of 30,000 U-boat crewman over almost six years
can seem acceptable, when an order of magnitude more were lost in
Stalingrad over six months. Donitz tried improved subs, radar detection
equipment, snorkels to keep out of sight, extending operations to new
areas where convoys were not in place or over confident, and dropping
wolf packs in favor of individual attacks. The result would be brief
periods of increased allied losses such as July of 43, and March of 44,
but after July 43, they never got above 20% of their Nov. 42 peak of
729160 GRT.
<https://en.wikipedia.org/wiki/Losses_during_the_Battle_of_the_Atlantic>
<http://www.naval-history.net/WW2CampaignsAtlanticDev.htm>

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

Fast ships, > ~18 knts, were largely regarded as safe from U-boats. Slow
boats in convoys largely safe. The rare slow boat detached from convoy
was regarded as vulnerable.

Were convoys still used to the end of the war?

The slower ships remained in convoys until a few weeks after Germany's
surrender. It took a while for word to get to all the U-boats.

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".