In the middle of 1942, the Allied navies in the Atlantic were facing a dire situation.
For the last six months German U boats had unleashed a devastating wave of sinkings
along the American East coast, pushing allied shipping losses in the Atlantic to record levels.
But over the next twelve months, in a colossal effort, the American and Royal Navies turned
the campaign around, culminating in a series of colossal convoy battles that crushed the
U-boat force, secured control of the Atlantic, and paved the way for Allied victory in world war 2.
1942 was a bad year for the Allies in the Atlantic. German U-boats had rampaged like never
before, and mo re than 5.4 million tons of allied shipping was sunk in the North Atlantic alone.
It was especially bad off the eastern seaboard of the united states, where American ships
were subject to an onslaught following their entry into the war in the dying days of 1941.
Whereas the British had learnt the hard way the value of keeping merchant
ships together in close formation, escorted by anti-submarine escorts,
it was a lesson which the US Navy, under Admiral Ernest King, had not yet fully taken on board,
and it was slow to provide sufficient escorts or an organised convoy system.
This meant there were hundreds of lone, unescorted merchant ships scattered up and down the coast at
any one time, making it almost trivial for German U-boats to attack. Between January
and June 360 Allied merchant ships were sent to the bottom in this part of the atlantic by
enemy submarines- of these, only a handful were sailing in convoy at the time they were sunk.
During this time, the bulk of the US Navy’s resources in both aviation and escort vessels
remained in the pacific, and it took until July, after a six-m onth masscacre on the east coast,
for the intervention of President Roosevelt to force Admiral King to divert resources to put
Atlantic traffic in convoy. After this, losses plummeted- 3 ships were sunk in this region in
July, and none thereafter for the rest of 1942. Instead, the U-boats shifted their focus back to
the mid-atlantic, plying their deadly trade again in the gap between air cover from east and west.
But as they did so, Donitz’s U boats found that their opponents had greatly strengthened.
During the six months when German focus was on the American coast, the Royal Navy had quietly
built up its strength. Dozens of flower class corvettes had entered service on top of the 118
commissioned in 1941, and many escorts had been refitted with more advanced radar and weaponry
like the hedgehog anti submarine mortar. In the air it was a similar story: RAF coastal commands
strength rose from 28 aircraft in July 1942 to 118 by the start of 1943, with new very long
range B-24’s being delivered possessing advanced Radar sets and weaponry to find and sink U-boats.
As well as possessing more and better weaponry,
the co-ordination between air and sea assets had improved dramatically by late 1942,
and as more and more liberty ships came into service so did the speed of Allied convoys.
The result of all of this was that Allied convoys became tougher to catch and tougher to attack,
and the number of ships proceeding independently dwindled. In August 1942 the number of ships sunk
in convoy exceeded that of those sunk unescorted for the first time- simply because there were so
few left sailing independently in the key battleground of the north Atlantic. The
efforts of three Allied navies had squeezed the space for the u boats to operate in and removed
the easy supply of prey- if the U boats wanted to do serious damage to allied trade in 1943,
they would have to do so by attacking these bigger and better escorted convoys head on.
They would do so at least with the largest fleet of U-boats yet. By the start of 1943,
the Kriegsmarine had 212 submarines operational, and in March 1943 made their first large scale
convoy attack of the year. 41 U boats were deployed in three wolfpacks, to intercept the
convoys HX229 and SC 122 as they crossed the mid Atlantic gap, totalling 110 merchant ships between
them. Over three days and nights a titanic battle took place in which 22 allied merchant
ships were sunk for the loss of just one U-boat. It was a striking success for the U-boats, and
raised the terrifying prospect in London that perhaps the German navy was now strong enough
to make convoy ineffective, which if true could destabilise the entire war effort. But in truth,
the fears were overblown. Even after the highest monthly losses of the entire war, 96% of those
that travelled in convoy in the first three months of 1943 arrived safely at their destination.
The size of the U boat force that had been committed to the battle was also not something
the Kriegsmarine could keep up constantly. Large numbers of boats had to return to port to rest and
rearm, and it took until the end of April for Admiral Donitz to deploy a large force, for a
second attempt at severing the Atlantic link, with 50 boats launched against Convoy ONS5. This time
though, the U-Boats would not get off so lightly. ONS5 was repeatedly attacked from April 29th –
6th May, losing 12 of its 43 merchant ships in the process. But its escorts,
under the leadership of 30-year-old Commander Peter Gretton, struck back hard, sinking seven
U-boats and seriously damaging seven others. It was a masterclass in convoy defence- utilising
all of the Allied technological advances in the shape of direction finding and radar, as well
as hundreds of hours spent relentlessly practicing tactics and co-ordination between escorting ships.
The reality was, for all the apparent success of March 1943, by that year the Atlantic had become
an incredibly lethal environment for U-boats, who were caught between powerful convoy escorts
and virtually omnipresent Allied air power across almost the entire ocean. By the end of what became
known as ‘Black May’, 43 U boats had been sunk and 73 more damaged. Though they had inflicted
casualties on the Allies, the losses were totally disproportionate. More U boats had been sunk in
one month than in the entirety of 1941, at a rate three times higher than any other month on record.
This is ofte n presented as the ‘turning point’ in the battle of the Atlantic,
but really it was the end of it. Faced with such colossal losses, Donitz had no choice
but to pull his boats back from further direct attacks on Allied convoys after May 1943.But
the brutal reality was that if they couldn’t attack convoys,
then the U boat arm no longer had any way of impacting allied merchant shipping. This was
immediately borne out in the statistics. Shipping losses plummeted to just 30,000 tons in June 1943,
and after a brief increase the following month, never again rose to even early war levels.
Indeed t he tables were soon turned completely, with U boats becoming the prey of new Allied
‘hunter-killer’ groups of escort carriers and destroyers. Harried and hunted by Allied air
and sea assets almost from the moment they left port, Donitz’s boats were unable to meaningfully
effect Allied shipping and began to suffer devastating losses even without large scale
battles. In the last two years of fighting from the start of May 1943, 554 U-boats were sunk.
It was a crushing and total allied victory. It was a victory not won in May 1943 but
over the course of four years preceding it, by shipyard workers, codebreakers, naval planners,
scientists and engineers, and the merchant and military sailors of dozens of nations, including
all the major powers. The dramatic events of ‘Black May’ did not decide the battle of the
Atlantic, but revealed who had already won it, through industrial and technological might.
But it was a victory won at huge materiel and human cost. By the m iddle of 1944,
20 million tons of Allied shipping had been sunk- 16m of it in the waters of the Atlantic. More than
46,000 civilian merchant sailors died on the allied side, at a casualty rate that was
much higher than those in the armed navies. It was even worse on the Axis side. The 762
total U boa ts lost had taken 28,000 men with them- a casualty rate of 75%, which was the the
highest of any branch of any armed service, anywhere in the world during world war 2.
Victory in the Atlantic in 1943 did not involve the destruction of a German Army
Group as Stalingrad did, or liberate vast swathes of territory as was happening in North Africa and
Italy, but it laid the logistical foundation for the enormous allied advances yet to come.
Control of the Atlantic allowed the unhindered transport of American troops and materiel for
the largest amphibious invasion in history in June 1944, and it enabled the shipments of huge
amounts of Lend Lease support to the Soviet Union. This included hundreds of thousands of trucks,
as well as the high-octane aviation fuel and aluminium critical for aircraft production- of
which the Soviets had little. This support played a key role in the transformation of
the Red Army into an offensive, mobile force capable of sweeping through Eastern Europe.
Allied victory in WW2, when it eventually came in 1945, was
built on a foundation laid in the Atlantic.