It’s safe to say the early part of the second world war did not go well for the
British Empire or its allies. But though defeats in Europe and the loss of France
as an ally were serious disasters, the top of Britain’s government remained in no doubt that
the greatest threat to their survival and the continuation of the war was to be found at sea,
in the form of German U-Boat submarines which for four long
years would terrorise the Atlantic and threaten the suffocation of Britain’s entire war effort.
The Second World War was only hours old when the U-Boat menace began to show itself. On the
evening of September 3rd 1939 the passenger liner SS Athenia was mistaken for a warship,
torpedoed and sunk by U-30 with the loss of 118 passengers and crew.
This was followed swiftly by the losses of the aircraft carrier HMS Courageous on
September 17th and battleship Royal Oak in an audacious raid on Scapa flow a few weeks later.
But the real danger to Britain was not the losses of these large capital ships,
but the sinkings of increasing amounts of civilian merchant ships- more than 200 of them by the end
of 1939. For Germany, the logic behind these attacks was brutally simple – sink the merchant
ships and you deprive Britain of the essential food and war materiel they carried. And if you
sink the merchant ships faster than the Allies could replace them, eventually Britain would run
out of ships, severing the link to the US and its colonies completely and crippling its war effort.
Keen to bring this about, Germany attacked merchant shipping with
a variety of different weapons, including aircraft, mines, disguised merchant raiders
and at various times the major surface ships of the kriegsmarine itself, with mixed results.
But overwhelmingly, the principal weapon in the war against Allied shipping was the submarine,
which ultimately accounted for 68% of Allied shipping sunk during the war.
In the early months of the war the U-Boat force under the leadership of Karl Donitz, found itself
tasked to support the invasion of Norway, but after that campaign concluded Donitz’s boats
were released into the Atlantic. Their crews were delighted to find large amounts of Allied shipping
sailing independently as Britain struggled to find enough convoy escorts to protect them all.
It did not take long for losses began to mount. 130 ships- more than half a
million tons of shipping – was sunk in the Atlantic and waters around Britain in June,
as the U-boat offensive added to damage done to British coastal traffic by mines and aircraft
As summer turned to autumn, the U Boats grew bolder, for the first time beginning
to co-ordinate their assaults, forming up as wolfpacks to attack Allied convoys
in night-time surface attacks. One of the first major targets was the slow west-bound convoy SC7,
which was mauled by a pack of U-boats led by Otto Kretschmer’s U-99 over three days in October 1940,
losing 20 of its 35 merchant ships. Shortly afterwards, the fast convoy HX79 was similarly
attacked, losing 12 out of 50 ships. These were terrible disasters for the Allies,
exposing poorly co-ordinated escort ships- of which there weren’t enough-, an over-reliance
on ASDIC sonar that could not detect a surfaced submarine, and merchant ships that were too slow.
By the end of the year, 3.6 million tons of allied shipping had been sunk in the North
Atlantic and the waters around Britain. This outstripped British merchant ship production
by almost three million tons for the year, even before adding losses suffered elsewhere.
It had been a brutal few months, and there was no let up in the new year,
with a new monthly record of 517,000 tons of shipping lost in March 1941.
Firmly on the back foot, the British scrambled to respond. New merchant shipping was ordered from
the US and as an escort stop gap 50 old American vessels were procured in the ‘destroyers for
bases’ agreement in September 1940. In British shipyards, dozens of flower class corvettes were
under construction and would join the fe w that were already in service, but these would take time
to build, and in the mean time prodigious numbers of merchant ships continued to be
sunk- with monthly losses still above 400,000 tons a month by June. The situation was dire.
But for the second half of 1941, the Allies had two breakthroughs which eased the pressure.
The first was the cracking of the German Naval Enigma code for the first time in early 1941 by
a team led by Alan Turing at Bletchley Park. This allowed the Allies to anticipate U-boat positions,
and route convoys around them for large parts of the rest of the war.
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The second major breakthrough for the Allies was the growing influence of the United States
on the Atlantic, even as they remained formally at peace with the Axis. After winning re-election in
November 1940, President Roosevelt implemented the Lend Lease Act to make it easier for the
British to obtain US supplies and approved the construction of a vast new class of merchantmen
that would come to be known as the ‘Liberty ship’. In April, the President went a step further and
authorized the US Navy to play a more active role in protecting American trade to Britain,
extending a ‘security zone’ to 26 degrees west and occupying Iceland. As German U-boats were
then operating as far west as 38 degrees, this brought American ships into potential conflict.
After the sinking of a US merchant vessel by a U-boat in May, and an attack on the destroyer
Greer in September, President Roosevelt issued a ‘shoot on sight’ order and the US Navy began to
directly escort Allied convoys through the western half of the Atlantic. This stretched the notion
of ‘neutrality’ to breaking point, and it did not take long for American ships to get caught
up in the fighting. On October 17th the destroyer Kearny was damaged during a battle with a U boat,
before two weeks later while escorting convoy HX156 near Iceland, the USS Reuben James was
torpedoed and sunk with the loss of 100 sailors. Despite this loss, the effect of the US’s
assertive protection of its trade, combined with gradually stronger British resources,
was to make life much tougher for the U-boats, who found fewer lone merchant ships and struggled
to continue their success in early 1941 for the rest of the year. Shipping losses
in the Atlantic dropped dramatically, down to just 85,000 tons in November- at a time
when the number of operational U-boats had almost quadrupled, from 22 in January to 80 by December.
This was an important Allied success, preventing a costly six months from becoming a devastating
year, but it still left Britain with a lot less shipping than before. Total tonn age lost during
1941 in the Atlantic was almost 3.3 million tons – again comfortably outstripping British production
even before factoring in losses in other theatres. And it was about to get much worse.
On December 10th 1941, Germany declared war on the United States in the aftermath of the
Pearl Harbour attack. For Admiral Donitz’s U-boat campaign, this was fantastic news- now his boats
were free to range across the Atlantic supported by new Type 14 fuel tanker submarines to attack
the vast amounts of American shipping sailing up and down its eastern seaboard and in the
Caribbean. And unlike the increasingly difficult to attack allied convoys in the mid-atlantic,
almost all of it was unescorted. Within weeks of war being declared,
Donitz’s boats unleashed a devastating wave of sinkings in the western Atlantic.
Tonnage lost in Janua ry more than trebled from November, and by the spring more than
half a million tons of merchant shipping was being lost in the Atlantic each month.
The US Navy, under its new commander in chief Ernest King, struggled to get to grips with
the problem, being slow to introduce convoys along their eastern coast and slow to provide
adequate escort vessels and air cover. And so the sinkings continued – peaking at more than 650,000
tons of shipping losses in June - 7 times more than November 1941.
At this point President Roosevelt intervened and ordered the navy to get its merchant shipping into
convoy. After they did, losses dropped sharply. But after six months of carnage, serious damage to
the Allied war effort had been done nonetheless. For example, of crucial concern to the US was
the tr ansport of Bauxite ore from British and Dutch Guyana, which was used to make the aluminium
needed for aircraft production. According to the historian Phillips Payson O’Brien,
General George Marshall, the US army chief of staff, reported in mid 1942 that 22% of the
US’s Bauxite transporting fleet was sunk between January and June. At around the same time, 1942
estima tes for US aircraft production were revised downwards from 60,000 to 48,000 aircraft – a drop
of 20% percent. O’Brien suggests that the German Navy could therefore be said to have ‘destroyed’
12,000 US aircraft, by preventing them from being built in the first place.
When you extrapolate this across all 6.1m tons of shipping that had been sunk in the Atlantic by the
end of 1942, you end up with huge amount of Allied guns, tanks and aircraft that never make it to the
front line in American, British or Soviet hands. And the impact of the U-Boats was not felt just
in the direct losses of materiel through sunken ships, but also in the colossal response they
provoked in the American war economy. Alarmed by the dangers of losing control of the Atlantic,
President Roosevelt intervened to prioritise aircraft and naval escort forces, ordering in
December 1942 that 462 escort vessels were to be built by the end of 1943. On top of this was
the massive ongoing expansion in merchant ship construction, with nearly a thousand
ships scheduled to be added in 1943 alone as the Liberty ship program came to fruition.
The resources for these enormous projects had to come from somewhere,
and they came from other parts of the US’s military buildup. According to O’Brien,
The proportion of war production allocated for the army dropped from 35% in January 1942 to
20% by December, with the planned size of the US army’s infantry force in 1943 cut by 40%.
The German offensive in 1942 in the Atlantic had struck a powerful blow against the Allies,
probably the most serious in the west since the fall of France in 1940.
They had sunk huge amounts of war materiel and forced their opponents to devote a colossal
amount of war production to counter the U boats in a quest to regain the upper hand.
With the ability of the US to build up strength in Europe, and supply Britain and the soviet union
with crucial war materiel at stake, It was a battle the allies could not afford to lose.
Over the next 12 months, they would make sure they didn’t.
Make sure you’re subscribed so you don’t miss the next video’s story of how they turned it around.