Defending the lifeline

When the war began the Royal Navy, with the help from Canadian, French and other Allied navies, took on the job of defending British and Allied merchant shipping from German attacks.   As in the later stages of the First World War (from 1917-1918), its main means of defence against such attacks was the convoy system.   This involved groups of merchant ships sailing in close formation under the protection of one or more escort warships.  When the war began, however, Britain and her allies had too few naval escort ships for ocean convoy work.   They also had too few long-range aircraft available to provide adequate air cover for Atlantic convoys.  

The convoys

From the first day of the war, the Admiralty organized most British and Allied ships crossing the Atlantic into convoys.  These originally consisted of up to 30 or 40 merchant ships sailing in lines or columns under the protection of one or more naval escort ships.   In later war years, Atlantic convoys became much larger, often exceeding 70 ships.

Convoys were the basis of an ‘interlocking system of shipping traffic’.  This meant that ocean convoys were distributed into coastal convoys for passage to and from UK East Coast and West Country ports.  Coastal shipping around less vulnerable parts of the British coast did not usually sail in convoy.

Western Approaches Command

Most ocean-going shipping travelled to and from Britain via her western coastal waters.   From October 1939 the defence of these waters came under the naval operational control of ‘Western Approaches Command’ headquarters, based at Plymouth.  In February 1941 these headquarters were moved to Liverpool, the largest and most central west coast port.  Thence it developed into a vast organisation, responsible for the day-to-day direction of Britain’s entire North Atlantic campaign.

Lack of escorts

At the outbreak of war, the Royal Navy was desperately short of ships suitable for convoy escort work.  It had available for convoy duties less than 24 old destroyers, a handful of sloops and a few anti-submarine trawlers.  In the winter of 1940 there were not enough escorts to provide two for each convoy and the Admiralty had to call on the services of 70 trawlers from the fishing fleets.  They also had too few long-range aircraft available to provide adequate air cover for Atlantic convoys.   This left a fatal ‘Air Gap’ in mid-Atlantic which the U-boats were to exploit with devastating effect during the early war years.

From August 1941 the need to protect the vital convoys to North Russia caused a further drain on the Royal Navy’s resources.  This was partly balanced by the growing role of the Royal Canadian Navy in the North Atlantic.

In September 1940, 50 old US destroyers were transferred to the Royal Navy in return for the gift or lease to the USA of British naval and air bases in the western Atlantic islands.  These old but sturdy ships were to do vital work in escorting Atlantic convoys.

Until July 1941 Atlantic convoys leaving or approaching Britain only had naval escorts within 150 miles west or south of Ireland.  For almost the first two years of war ships were usually unescorted for the greater part of the Atlantic crossing.

Towards the end of 1939 incoming Atlantic convoys were singled out for attack by German U-boats.  The most critical time was after the division of a convoy west of Ireland, when small groups of ships would sale for port with only one destroyer to each group.  The 8,000 ton ‘Malabar’ was torpedoed by the German submarine U-34 some 50 miles west of the Scilly Isles in the early hours of 29th October 1939.  She sank the following afternoon.  ‘Malabar’ had left convoy HX5 (Halifax, Nova Scotia to Britain) to take the southern route around Ireland in the company of an oil taker and the destroyer ‘HMS Grafton’.  She had been bound for London and Avonmouth with tobacco, lumber and general cargo.   Five out of her crew of eighty-one were lost.

The 'Flower-class' corvette, Royal Navy

On the outbreak of war, Churchill, the First Lord of the Admiralty, gave top priority to an emergency programme for the production of new ‘Flower-class’ corvettes (names after flowers) as convoy escorts.  Based on a whalecatcher design, these ships were simple and cheap to build.   First coming into service in April 1940, they bore the brunt of British and Canadian naval escort work in the Battle of the Atlantic.  Nearly 300 were built, and they sank 38 U-boats for the loss of just 25 of their own number.

The corvettes and other British escort ships in the Atlantic were often manned largely by wartime or ‘hostilities only’ sailors.   These men, whether conscripts, volunteers or naval reservists, learned their new jobs remarkably quickly. The Royal Navy Volunteer reserve, 6,000 strong in 1939, was the Navy’s second line of reserve.  Unlike the Royal Navy Reserve, it consisted of volunteers with no professional sea experience or training.

The Liverpool-born author Nicholas Monsarrat, son of a Rodney Street surgeon, was a young Lieutenant, RNVR (Royal Naval Volunteer Reserve), on board the corvette ‘HMS Campanula’ from 1940 until early 1942.  During the war, Monsarrat drew on his experiences on ‘Campanula’ to write his book ‘HM Corvette’ (1942).  Later, he also used his ‘Campanula’ memories as background material for his best-selling novel ‘The Cruel Sea’.

"A corvette would roll on wet grass." HM Corvette (1942)

"They were at sea for twenty-two days on that trip: at the end, Compass Rose, and her crew with her, looked as if they had all been through a tidal wave, emerging in tatters at the end of it." The Cruel Sea (1951)

The Navy’s ‘underwater ear’

By 1939 the Royal Navy had fitted many of its smaller warships with Asdic, later known to the US Navy as sonar.  This was secret apparatus for locating submerged submarines by using sound waves.  The device consisted of an electronic sound transmitter and receiver, housed in a metal dome and fitted beneath the ship’s hull near the bow.  The transmitter sent out high-frequency beams – audible ‘pings’ – that bounced back when they hit an object.  These echoes were heard by an operator who wore earphones and watched the sound waves traced by a pen on a moving sheet of paper.  The time that passed before an echo was received showed the range of an object: the pitch of the echo revealed whether it was approaching or moving away.

Asdic's weaknesses

Before the war, the Admiralty had confidently claimed that with Asdic “one destroyer could do the work of a whole flotilla” in anti-submarine warfare.  But under war conditions the apparatus proved to have serious limitations.  It gave only the compass bearing of a U-boat, and not its underwater depth.   It was limited to searching with a narrow beam at a fixed angle and at a range often less than a mile.  It was seriously disturbed by the rough water and by speeds above eight knots.   Weeks of combat experience and a keen ear were needed for a seaman to use Asdic equipment effectively.

Nevertheless, the Royal Navy were to sink a number of U-boats using Asdic.  And at the peak of the Battle of the Atlantic many U-boats were put off from attacking convoys when their crews heard the ‘pings’ of enemy hunters moving towards them.

The depth charge

Until 1942 the depth charge was the only weapon which could be used against a submerged submarine.  It consisted of a steel drum filled with 300 pounds of high explosive which could be set to detonate at various depths.

In 1939 the standard equipment for small warships was a trap from which charges were rolled over the stern and two mortars, or throwers, which fired them 120 feet on either beam.   Soon, more traps and throwers were added.  Depth charges were dropped in various patterns, to give the best chance of success.  Eventually, heavy weights were bolted to half the charges, causing them to sink faster and explode deeper.

The depth at which a charge exploded was controlled by the rate of water flow through a preset valve at one end.  After filling a pistol bellows chamber, the water drove the detonator against the primer, causing it to explode and set off the main charge.  An exploding charge could destroy a U-boat 25 feet away and damage one 50 feet away.  Even explosions that did not damage their targets could cause trauma similar to shell shock among U-boat crews.

Self-defence for Britain's merchant ships

As early as 1937 Merchant Navy defence courses had been organized at major British ports to train officers in gunnery and convoy work, and to teach seamen to be gunners.   The fitting of guns on merchant ships started on the day war began.  By the end of 1939, 1500 ships had been armed with anti-submarine guns, rising to 4,000 a year later.

At first, the job of manning the guns on merchant ships fell largely to naval reservists of the DEMS (Defensively Equipped Merchant Ships) organisation, set up by the Admiralty at the start of the war.   As U-boats attacks increased, however, thousands of merchant seamen also became skilled in handling guns and other armament.  By 1942 they were often joined on the most threatened routes by Army machine-gunners of the specially created Maritime Regiment of the Royal Artillery.

Defence against mines

From the early months of war the approaches to all main British ports were regularly swept for mines by the large fleet of Royal Navy minesweepers.  This relentless and highly dangerous work was carried out by many kinds of vessel, including converted trawlers.  In the River Mersey and its approaches, for example, minesweeping was done by former Fleetwood trawlers based at Wallasey Dock, Birkenhead.

From mid-1940 onwards the hulls of most large British ships were fitted with degaussing cable, which greatly reduced the Threat of German magnetic mines.  Degaussing was a method neutralizing a ship’s magnetism by passing an electric current through a cable fitted around the top of a ship’s hull.

HM Rescue Tugs

The Royal Navy’s Rescue Tug Section was set up at the start of the war to provide suitable ocean-going tugs to help save torpedoed ships.  Originally only four Royal Navy tugs and eight ‘civilian requisitions’ were available for deep-sea work.  By the end of the war, however, due to newly-built additions from British and US shipyards, their number had grown to over eighty.

The Rescue Tugs were largely manned by Merchant Navy crews, serving under Royal Navy orders.  From 1941 they were based at Campbeltown, South-west Scotland, and from May 1943 a rescue tug was attached to every transatlantic convoy.   By the end of the war the ’Campbeltown Navy’ had helped to save over three million tons of Allied shipping, over 250 warships and hundreds of Allied seamen, mostly in the North Atlantic.  Twenty rescue tugs were lost on active service.

The CAM Ships

 From the summer of 1941 onwards Britain converted 35 newly-built cargo ships into ‘Catapult Aircraft Merchantmen’ (CAM) ships.  Each of these was able to launch a Hurricane fighter aircraft via a ‘rocket-propelled trolley catapult’ to protect a convoy from air attack.  The Hurricanes were usually manned by Royal Air Force pilots from the Merchant Ship Fighter Unit, based at RAF Speke, near Liverpool.

Unfortunately, such ships had no flight decks on which the aircraft could land, and so each fighter would be ditched into the sea and allowed to sink after just one mission.   Although rarely launching their aircraft, between 1941 and mid-1943 (when they were withdrawn from service) these ships were a useful deterrent against enemy aircraft on Atlantic, Gibraltar and Arctic routes.

Escort groups

The establishment early in 1941 of the Western Approaches Command Centre in Liverpool under Admiral Sir Percy Noble brought a sudden improvement in British fortunes in the Atlantic campaign.  Noble saw the need to make the best use of the few escort ships available to him.  He therefore ordered the formation of Escort Groups which were rigorously trained in anti-submarine tactics at Tobermory in Scotland.  By mid-March 1941 the new-found skill and morale of the escorts had been rewarded by the sinking of four U-boats in ten days and the elimination of three of Germany’s most successful U-boat commanders.

Defeat of the Aces

On the night of 16 March 1941 Captain Donald Macintyre’s 5th Escort Group, led by his destroyer ‘HMS Walker’ defeated a ‘wolf pack’ attack on convoy HX 122 south of Iceland and destroyed two U-boats.   This finished the spectacular careers of two of Donitz’s leading Aces, namely Joachim Schepke and Otto Kretschmer.  Schepke was crushed to death when U-100 was rammed and Kretschmer was captured after U-99’s golden horseshoes finally ran out of luck.  A third Ace, Gunther Prien, who had sunk the ‘Royal Oak’ at Scapa Flow, had been lost with U-47 in combat with another escort group several days earlier.

The secret victory

In early May 1941, Royal Navy escorts achieved a crucial victory in the Battle of the Atlantic, which was to remain a closely guarded secret for thirty years.  On 8 May a skilful attack off Greenland ended the career of U-110 and the life of Kapitanleutnant Lemp, who had sunk the ‘Athenia’.  The rush to abandon U-110 allowed a boarding party from ‘HMS Bulldog’ to capture the U-boat as well as her code books and Enigma machine before she sank.  This gave British cryptoanalysts their first change to break the complicated U-boat codes.

Commander Roger Winn, in charge of the Admiralty’s Submarine Tracking room in London, gained a vital source of information regarding U-boat positions and tactics due to the Enigma breakthrough.  In future, convoys could often be safely guided away from U-boats, or reinforced if threatened.

The 'Bismarck' action

Admiral Raeder, Commander-in-Chief of the Kriegsmarine, hoped that a spectacular break by a powerful surface force into the Atlantic would be a decisive effect on the war at sea.  Hitler expressed serous doubts, but in late May 1941 the giant 42,000 ton battleship ‘Bismarck’ sailed from Norway with the heavy cruiser ‘Prinz Eugen’ for operations against North Atlantic Convoys.  The ‘Bismarck’, even by herself, presented a formidable naval threat.   One of the most powerful warships afloat, she had four, twin, 15-inch gun turrets firing high speed shells with the aid of a radar-guided aiming system.  Special Krupp ‘Wotan’ armour shielded her decks and hull.   She was also divided into so many ‘watertight’ compartments that her crew believed the ship to be ‘unsinkable’.

The ‘Bismarck’s dramatic Atlantic sorties caused great anxiety to Britain.  In a brief action off Iceland she sank the old British battlecruiser ‘Hood’, with the loss of more than 1400 lives, and damaged the new battleship ‘Prince of Wales’.  There then followed a frantic search by forty-six British and Allied warships and many aircraft before the German super-battleship was finally tracked down and sunk. 

The sinking of the ‘Bismarck’ in May 1941 largely ended the threat of German surface warships in the Atlantic. In just over an hour on the morning of 27 May 1941 the battleships ‘HMS Rodney’ and ‘King George V’ pounded the crippled ‘Bismarck’ into a blazing wreck by the combined weight of their 16 inch and 14 inch guns.  After being torpedoed by the cruiser ‘HMS Dorsetshire’, the ‘Bismarck’ finally capsized and sank with her colours flying.  Of her ship’s company, over 2,000 were lost and only 118 saved.