The Real Cruel Sea: The Merchant Navy in the Battle of the Atlantic 1939-1943 by Richard Woodman

Author:Richard Woodman [Woodman, Richard]
Language: eng
Format: azw3, epub
ISBN: 9781844689750
Publisher: Pen and Sword
Published: 2011-07-06T04:00:00+00:00

PART FOUR

January–July 1942

WEAKNESS IN

DEFENCE

15

‘Presented to us on a plate’

Liberty ship

THE JAPANESE ATTACK by carrier-borne aircraft on American warships at Pearl Harbor on Sunday 7 December 1941 owed much to two British precedents. The first was a pre-emptive strike by a powerful British force on the Danish capital, Copenhagen, in 1807, the purpose of which was to deny Napoleon the use of the Danish fleet; significantly, it was made without any declaration of war. The second was the British Fleet Air Arm’s attack on the Italian Fleet at Taranto in June 1940.1

The attack on Pearl Harbor brought to a head the policies of both Roosevelt and Churchill, for at a stroke the American people were outraged. Where the capture of the United States merchant ship City of Flint by the Deutschland in December 1939 had entrenched the isolationists and strengthened the hand of those pressing for the Neutrality Act, the wholesale bombing of United States battleships was seen without equivocation as casus belli. It meant that Great Britain would no longer bear the brunt of the war, and while the participation of the United States Navy, in its own version of ‘phoney war’, had already proved of the utmost importance in easing the Royal Navy’s burden, it was felt that its wholehearted support would prove decisive.

But while the Grand Strategists in London might breathe a sigh of relief, those more intimately concerned with grey-water strategy had a crisis yet to face, and for those involved with tactical action at sea there were months of steadfast attrition by the enemy to come. All the benefits of Ultra decrypts notwithstanding – and they could be intermittent, and fail at critical moments – the ability of the German’s B-Dienst service to read British naval signals and monitor British naval movements was fatal to the Allied interest. From 1934 the B-Dienst under Kapitänleutnant Heinz Bonatz had maintained a close watch on British and French developments, and by the summer of 1939 some five hundred operators in sixteen stations were engaged in this task.

The British Admiralty used two encrypting mechanisms, the Naval Cypher for operational signals and the Naval Code for administrative purposes, which in due course included ship movements. Both used numerical encoding, and were then super-encyphered by means of complex tabulations which changed regularly. But the Naval Code had been used before the war without this latter refinement, and it had been easy to break by comparing the encoded reports emanating from merchant ship movements with accounts of their passages published by Lloyd’s of London. At the time of Mussolini’s invasion of Ethiopia the Admiralty had begun to super-encypher the Naval Code in the same way as the Naval Cypher, and this had enabled the B-Dienst cryptanalyst Wilhelm Tranow to crack the latter by way of the former. By the time of the Norwegian Campaign of 1940 Tranow and his colleagues could expect to read up to half the Allies’ radio traffic, enabling the German navy to evade British concentrations.

By March 1940 the British

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