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HMS Stanley, ex-US flushdeck destroyer (Courtesy Cyberheritage), one of 50 transferred to Britain from September 1940 in the "Ships-for-Bases" deal. These helped filled a gap in Britain's U-boat defences at a crucial time.

Politically dangerous to President Roosevelt, the deal was a major move in America from isolationism towards war.

Many such exchanges took place between the two nations - ships, aircraft, guns, radar, aero-engines, intelligence, code-breaking, atom bomb developments ......



German Codes - The British Code & Cipher School moves to Bletchley Park, England, the site of its magnificent successes breaking the German Enigma codes through the 'Ultra' programme . The school builds on the work of Polish and later French code-breakers. By April 1940 the first low level Luftwaffe codes are being deciphered. Many months follow before comparable progress is made with Naval codes.


Americas - The Pan-American Conference establishes a 300-mile plus security zone off the coasts of the Americas within which all hostile action by the belligerent powers is forbidden.


United States - The Neutrality Act is amended to allow the supply of arms to belligerents on a 'cash and carry' basis. At the same time American shipping is banned from the war zones.

Battle of the Atlantic - RAF Coastal Command continues to patrol for U-boats on passage into the Atlantic. Equal priority is now given to attacks, but the crews are not trained and lack effective anti-submarine bombs.

Magnetic Mines - German seaplanes lay the first magnetic mines off the East Coast and drop one on tidal flats at Shoeburyness in the Thames Estuary. It is defused on the 23rd November and recovered by Lt-Cdr Ouvry (awarded the George Cross), a vital step in the battle against a weapon which is causing heavy losses and long shipping delays. In November alone, 27 ships of 121,000 tons are sunk and for a time the Thames Estuary is virtually closed to shipping.



MARCH 1940

Canadian Politics - William MacKenzie King, Prime Minister of Canada is reelected by a massive majority in support of the government's war policies.

Merchant Shipping War - Since September 1939, 430,000 tons of shipping have been sent to the bottom by mines around the coasts of Britain - a loss rate only second to U-boats. Now the Royal Navy slowly counters magnetic mines with the introduction of ship-degaussing and 'LL' minesweeping gear. Although mines, contact, magnetic and later acoustic remain a threat throughout the war, they never again represent the danger of the first few months. Later in the year, fast, heavily armed and efficient diesel-engined German E-boats commence attacks in coastal waters. (Enemy or E-boat is the English term for German motor torpedo boats or S-boats - "Schnell" - not to be confused with the heavily armed torpedo boats or small destroyers with their 'T' designation.)

APRIL 1940

Atomic Bomb - Just as the “phoney war” ends in Europe (it never existed at sea) the end of the war is foreshadowed when the British government establishes the Maud Committee to oversee nuclear research. Similar steps have already been taken in the United States, all of which eventually lead to an operational atomic bomb.

German Codes - The Bletchley Park Ultra programme is now decoding some Luftwaffe low-level Enigma codes, partly because of poor German security procedures. There is little evidence the hard-won information influences the war over the next two violent months.

Air War - The first mines are laid by RAF Bomber Command off the German and Danish coasts.

MAY 1940

British Politics - Following a 10th May House of Commons debate on the Norwegian campaign, Prime Minister Neville Chamberlain resigns and Winston Churchill assumes leadership.

JUNE 1940

German Codes - 'Ultra' is now breaking the Luftwaffe Enigma codes with some regularity, and early in the month has its first major breakthrough when supporting evidence for the Knickebein navigation aid for bombers is obtained. Army codes are more secure because of the greater use of land lines for communications, and the Naval ones will not be penetrated until mid-1941.


British Scientific Developments - A British scientific mission carries to the United States details of many important developments. Amongst these is the recently invented cavity magnetron, vital for short wavelength radar and the eventual defeat of conventional U-boats. Also for the close-proximity fuse which becomes so important in the 1945 battles with Japanese Kamikaze aircraft. (The cavity magnetron is now the heart of the common microwave cooker!)

Battle of the Atlantic - Long range Focke Wulf Kondor bombers start patrols off the coast of Ireland from a base near Bordeaux. As well as spotting for U-boats they attack and sink many ships, and continue to be a major threat until the introduction of ship-borne aircraft in late 1941 starts to counteract them.

Royal Navy Codes - These are changed and for the first time RN operational signals are secure from German interception and decoding. it will be another three years before the convoy codes are made safe from the German


United States - After months of negotiations, a "Ships-for-Bases" agreement is announced on the 5th for the transfer of 50 old but valuable US destroyers to the Royal Navy in exchange for British bases in Newfoundland, Bermuda, the West lndies and British Guiana. The first of the "flushdeckers" arrive in Britain towards the end of the month.

Battle of the Atlantic - The German decoding B-Service is instrumental in directing U-boats to convoys, where they hold the advantage as they manoeuvre on the surface between the merchantmen and escorts. Radar is urgently needed so the escorts can detect the U-boats, force them to dive and lose their speed advantage. Then start hunting them with ASDIC.

Axis Powers - Germany, Italy and Japan sign the Tripartite Pact in Berlin on the 27th. They agree to jointly oppose any country joining the Allies at war - by which they mean the United States.


United States - Franklin D. Roosevelt is elected to an unprecedented third term of office as President of the United States.

Battle of the Atlantic - Important steps are taken in the air war when an RAF Sunderland equipped with 1.5m wavelength anti-surface vessel (ASV) radar locates a U-boat. This is the first success of its kind with a system that is mainly effective by day; contact is lost within two miles of the target. It is the addition of the Leigh light that will turn it into a powerful night-time weapon as well. Now Coastal Command is using depth charges instead of ineffective A/S bombs.

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Merchant Shipping War - Losses due to air attack and mines remain a major problem. Aircraft and E-boats have now added acoustic mines to the magnetic and moored contact mines in their armoury, but they never match up to the threat the magnetic mines represented a year earlier.

MARCH 1941

United States - The Lend-Lease Bill is passed into law. Britain and her Allies will be able to receive American arms and supplies without immediate payment.

Battle of the Atlantic - On 6th March 1941, faced with the mortal threat of the German U-boat and aircraft offensive in the Atlantic, Winston Churchill issues his famous Battle of the Atlantic directive. Catapult armed merchantmen (CAM) are to be fitted out, merchant ships equipped with AA weapons as a first priority, and more Coastal Command squadrons formed and fitted with radar. Port and dockyard congestion is to be dealt with and the defence of ports greatly improved.

Merchant Shipping War - Royal Navy motor gun-boats (MGB's) are entering service to combat E-boat attacks on East Coast convoys. Improved motor torpedo boats (MTBs) are also being built to attack German coastal shipping. This marks the first step in the building up of Coastal Forces.

Battle of Cape Matapan - As ships of the Mediterranean Fleet cover troop movements to Greece, 'Ultra' intelligence is received reporting the sailing of an Italian battlefleet with one battleship, six heavy and two light cruisers plus destroyers to attack the convoy routes. In the battle that follows, Italian battleship "Vittorio Veneto" is damaged and heavy cruisers "FIUME", "ZARA","POLA" and destroyers "ALFIERI" and "CARDUCCI" sunk for the loss of one Royal Navy aircraft.

Eastern Europe and Balkans - Bulgaria joins the Tripartite Pact on the 1st March and German troops march in. As of now, only Yugoslavia in the Balkans retains national independence for a few days more. On the 25th Yugoslavia joins the Tripartite Pact, but two days later an anti-Nazi coup topples the Government.

APRIL 1941

Battle of the Atlantic - Over the next few months a number of long awaited ship types and weapons start to be introduced. These will contribute significantly to the eventual defeat of the U-boat.

(1) The first Auxiliary Fighter Catapult Ships flying the White Ensign and equipped with a single 'one-way' Hurricane are ready in April 1941. In May a Hurricane is successfully launched from a Red Ensign Catapult Armed Merchantman (CAM). CAM-ships are eventually superseded in 1943 by Merchant Aircraft Carriers (MACs) - merchantmen with full flightdecks, but sailing under the Red Ensign and also carrying oil or grain.

(2) The final step in the introduction of ship-borne aircraft into the Battle of the Atlantic comes in June when the first escort carrier is ready for service. HMS Audacity, converted from a German prize, has a short life, but proves the great value of these vessels.

(3) New scientific developments also start to play their part. In May the first high definition, 10cm radar (Type 271) is installed in a corvette. Later still, high frequency, direction finding (HF/DF or 'Huff-Duff') is introduced to supplement the work of the shore stations.

MAY 1941

Capture of "U.110" and the German Enigma - South of Iceland, "U.110" attacks Liverpool-out convoy OB318. Blown to the surface by depth charges from corvette "Aubretia" on the 9th, "U-110's" crew abandon ship, but she fails to go down. A boarding party from destroyer "Bulldog", led by Sub-Lt Balme, manages to get aboard. In a matter of hours they transfer to safety "U-110's" entire Enigma package - coding machine, code books, rotor settings and charts. The destroyer "Broadway" stands by during this hazardous operation. Two days later "U-110" sinks on tow to Iceland, knowledge of her capture having been withheld from the crew. The priceless Enigma material represents one of the greatest intelligence coup ever and is a major naval victory in its own right.

"U-110's" capture is far and away the most successful of the attempts to capture Enigma codes. In the March 1941 raid on the Norwegian Lofoten Islands, spare coding rotors were found. Then two days before the "U-110" triumph, a cruiser force had tried to capture the weather trawler "Munchen" off Iceland. At the end of the coming June a similar operation is mounted against the "Lauenberg". In both cases useful papers are taken but the real breakthrough only comes with "U-110". Included with the material captured are all rotor settings until the end of June 1941.

A number of codes are used with Enigma. The U-boat one is 'Hydra', also used by all ships in European waters. From the end of June, Bletchley Park is able to decipher 'Hydra' right through until the end of the war. Unfortunately the U-boats move off this version to the new 'Triton' in February 1942. The big ship 'Neptun' and Mediterranean 'Sud' and 'Medusa' codes are also soon broken.

Germany - Rudolf Hess, Hitler's deputy, flies to Britain on his self-appointed peace mission. He is imprisoned in Britain and disowned by Germany

JUNE 1941

Atomic Bomb - The report on nuclear research by the Maud Committee leads to the setting up of a development programme by Imperial Chemical Industries. Code named 'Tube Alloys', it will oversee both atomic bomb and reactor work.

Battle of the Atlantic - Following the capture of the “U-100” Enigma material, the Royal Navy tracks down the supply ships already in position to support the "Bismarck" as well as other raiders and U-boats.

JULY 1941

Battle of the Atlantic - Air cover from Ireland, Iceland and Newfoundland is improving, but RAF Coastal Command lacks the long-range aircraft to cover the mid-Atlantic gap. It is in this area, some 800 miles long the U-boats are now concentrating. Between January and June 1941, North Atlantic merchant shipping losses had averaged 300,000 tons per month. From July to December 1941 they are considerably down at an average level of 104,000 tons. The reasons are varied - evasive convoy routing and more effective aircraft deployment from the 'Ultra’ work, introduction of radars and high frequency direction finding (HF/DF), the availability of more escorts, and continuous escort. Operational research or "OR" (Operations research in the US) using the simplest of mathematical techniques makes great contributions to the analysis of more effective convoy sizes, escort numbers, U-boat search techniques, depth charge patterns and settings etc.


Anglo-US Talks - Winston Churchill crosses the Atlantic in battleship "Prince of Wales" to meet President Roosevelt off Argentia, Newfoundland between the 9th and 12th. Together they draft the Atlantic Charter setting out their aims for war and peace. This is signed by Britain, the United States and 13 Allied governments in September.


Battle of the Atlantic - Escort carrier "Audacity" sails with UK/Gibraltar convoy OG74. Her American-built Martlet fighters shoot down the first Kondor to fall victim to an escort carrier, but U-boats still manage to sink five merchantmen. With major new U-boat construction programmes, the increased number of submarines available to Adm Doenitz (approaching 200 with 30 operational) allows him to establish patrol lines in the Atlantic.


Japan - War Minister Gen Tojo becomes Japanese Prime Minister.

Australia - The Country Party of former Prime Minister Robert Menzies who resigned earlier in August falls from power. John Curtin and the Labour Party takes over.


Battle of the Atlantic - RAF aircraft of Coastal Command are now flying regular patrols in the Bay of Biscay equipped with effective airborne depth charges and the long wavelength ASV radar. The first success is on the 30th by a Whitley of No 502 Squadron. "U-206" on passage to the Mediterranean is detected and sunk


Underwater Warfare - Three Italian human torpedoes launched from submarine “Scire” (Cdr Borghese) penetrate Alexandria harbour. Their charges badly damage battleships “Queen Elizabeth” with Adm Cunningham on board and “Valiant”. They both settle to the bottom and the Mediterranean Fleet battle squadron ceases to exist.

As the Imperial Japanese Navy goes to war, they introduce the Allies to a secret and powerful weapon in the 24in Long lance torpedo, with its far heavier warhead and range than any other.