Merchant Navy Supply Ships
(profile contributed by Justin "LooseCannon" Riggir)

"The Battle of the Atlantic was the dominating factor all through the war. Never for one moment could we forget that everything elsewhere depended on its outcome." Winston Churchill


The view across the columns of a convoy as seen from an AA gun position

During World War II the aircraft carrier came to eclipse the battleship in the rank of capital ships, however the most important ship remained the humble merchantman. The Battle of the Atlantic was unlike any other battle of the war, in that it was a campaign lasting five long years and the most important battle for the Allies, for until it was decided in their favor, their strategic plans could not be put into operation. If the Allies had failed to gain control of the Atlantic, Germany would have remained in control of Western Europe and the Mediterranean.

With warfare becoming dependent on logistics and the Royal Navy out-gunning the Kriegsmarine by the ratio of ten to one in capital ships, it was on the U-boat, and to a lesser degree the surface raider, that Germany's hopes of evading the Allied blockade and severing Britain's maritime supply depended. By the end of 1939, U-boats had sunk 114 ships with a tonnage of 421,156 for the loss of nine of their number. Given the small strength of the escort forces these figures could be considered satisfactory. However Germany was known to have begun a large scale construction program of U-boats, and it was projected that by 1941, at the latest, her number of operational submarines would be doubled or even trebled, and as the war lengthened these numbers would be progressively increased.


The British CAM-ship Empire Faith

With the German occupation of the airfields of western France and Norway, long-range Focke-Wulf Condor aircraft could search the Atlantic for British convoys and report their positions to the waiting U-boats. To counter this threat a few merchantmen were fitted with catapults to launch a Hurricane fighter and one of these ships would be included in the more important convoys. When a Condor was sighted, the Hurricane was launched via the catapult to engage and returned to ditch beside a merchantman to enable the rescue of the pilot. These catapult-armed-merchant ships, or CAM-ships, were in time replaced by the merchant-aircraft-carrier, or MAC-ship. These were usually a tanker with a full flight deck built over her normal deck, and carried around six fighters. The CAM-ships were replaced by auxiliary carriers, which were merchantmen converted into full aircraft-carriers with wooden flight-decks.

Shipping losses to December 1940 to U-boats alone were 2,606,000 tons, and when mines, bombers, surface raiders and E-boats were included the total rose to 4,523,000 tons. Losses of this magnitude were beyond the replacement capacity of the British shipyards - 40,000 men were released from the armed forces to be returned to the shipyards and docks to clear the huge backlog of 800,000 tons of shipping awaiting repair - and although there was still ample pre-war tonnage afloat under British flag, with the peak of the U-boat strength yet to be reached these figures were clearly ominous. The merchantmen losses from all causes in 1941 were 1,299 ships totalling 4,328,558 tons, an overall loss well beyond the Allies capacity to replace. Of even greater magnitude were the losses of 1942, with U-boats alone exceeding the total losses for 1941 by nearly 2,000,000 tons - 6,226,215 tons - the total loss for the year being 1,664 ships totaling 7,790,697 tons.

The German High Command had calculated that an average loss of 800,000 tons of Allied shipping per month would be enough to ensure an Axis victory, and optimistic reports on estimated tonnage sunk by individual U-boat commanders had led them to believe this was being achieved. The true overall rate of loss throughout 1942 was just under 650,000 tons, a crippling rate and far beyond the Allies replacement capacity, and throughout the grim months of 1942, defeat in the Atlantic, and thus the war, was a thought that haunted the Allies leaders. As serious as the loss of essential imports was the reduction in the rate of the building up of forces in Britain for the assault on Europe, and final victory over Germany.

Although Britain's shipyard output had been dramatically increased from the pre-war slump conditions with new intensive shift conditions, manning levels increased, skilled shipwrights exempted from military service and large numbers of women recruited, their output was limited to a maximum of 1,250,000 tons per year. In February 1942, the United States set themselves the ambitious goal of 24,000,000 tons of new ships before the end of that year. To meet this quota of 750 ships for 1942 and around 1,500 ships in 1943, United States yards would have to increase their output of ships from one to three per day. A government-sponsored program had been initiated to build more shipyards and by war's end 99 new yards with a total work force of over 1,500,000 were in operation. However, more yards alone would have never have been enough and an entirely new method of shipping construction was found. Borrowing from the mass-production techniques of the car industry, this method used all-welded construction, prefabrication and a standard design. This principal standardized ship was the 10,000 ton Emergency Cargo 2/large capacity, or EC2, and was based on a British tramp steamer designed in 1879, and was known as the Canadian Park and the United States Liberty ship.

The first Liberty ship, the SS Patrick Henry, was launched by the Bethlehem-Fairfield Yard of Baltimore on September 27, 1941 and a total of 2,700 would be built in the United States. Training schools for the platers, welders and shipfitters were established and thousands of women were employed. The ship yards were paid a fast delivery bonus of between $60,000 and $140,000 for each $1,500,000 ship. The construction time of six months for the first Liberty ship was cut back to two months per ship by mid-1942, and finally to just over a month. The Kaiser Corporation achieving record construction time when No: 440 was completed in four days fifteen hours on November 8, 1942. Three days later the SS Robert E Peary was loading her first cargo. In addition to their crew, the Liberty ships were manned by Naval Armed Guard gunners, the Park Ships were manned by Naval Volunteers who were known as Defensively-Equiped-Merchant-Ship, or DEMS gunners, who were assisted by the merchant seamen.


The Liberty ship SS John W Brown

Typical Liberty Ship Specifications
Displacement: 10,000 tons standard; 5 holds with over 9,000 tons capacity
Dimensions: 441 x 56 feet
Propulsion: 3 cylinder, reciprocating steam engine, 2,500 hp, 11 knots
Crew: 44 and between 12 to 25 Naval Armed Guard
Armament: 1 x 4 inch stern gun, 2 x 37 mm bow guns, 4 x .50 cal machine guns , 2 x .30 cal machine guns

In addition to the cargo carried in her holds, a Liberty ship would also carry freight such as aircraft, armoured vehicles, and locomotives lashed to her decks. The Liberty ship could carry 2,840 jeeps, 440 tanks, or 230 million rounds of rifle ammunition. The Liberty ship having a maximum speed of only eleven knots was of relatively easy prey for the U-boats and in early 1942 designs for a 15 knot ship, the Victory ship or VC2, were begun. The first of the 534 Victory ships built, again using the mass-production techniques of the car industry, the SS United Victory was launched on February 28, 1944. In comparison to the Liberty Ship, the Victory ship was of sleek lines and her hull was strengthened.


The SS United Victory being fitted out

Typical Victory Ship Specifications
Displacement: 10,000 tons standard; 5 holds with over 9,000 tons capacity
Dimensions: 455 x 62 feet
Propulsion: cross-compound steam turbine developing 6,000 or 8,500 hp , 15 knots
Crew: 44 and between 12 to 25 Naval Armed Guard
Armament: 1 x 5 inch stern gun , 1 x 3 inch bow gun , 8 x 20 mm cannon

Tankers had been developed around the turn of the century to carry bulk liquid cargo. During World War II the T-2 was the workhorse of the tanker fleet and in 1943 'skeleton decks' were attached about 7 or 8 feet above the decks to enable tankers to carry carry planes and PT boats in addition to their bulk liquid cargo. Tankers were always a prime U-boat target.


The SS Mission Purisima above, and to the right, aircraft lashed to a tanker's skeleton decks

Typical T-2 Tanker Specifications
Capacity: between 90,000 to 140,000 barrels
Dimensions: 523 x 68 feet
Propulsion: Turbo-Electric propulsion , 6,000 hp , 16 knots
Crew: 42 and 17 Naval Armed Guard

Images of the SS John W Brown, SS United Victory, SS Mission Purisima and skeleton decks, kindly provided by US Merchant Marine - A site dedicated to the Mariners who died in service of their country during all Wars

Sources: Purnell's History of the Second World War, World War II Orbis Publishing and The Battle of the Atlantic by John Costello and Terry Hughes