"Battle of the Atlantic"
1940 ~ 1945
The Battle of the Atlantic was a series of many deadly engagements covering some four million square miles of ocean and lasting five long years. Victory meant supreme control over North Atlantic shipping. The German U-boat, tried to sink allied shipping at a rate faster than replacements could be constructed. During 1941 and 1942, for example the German Navy sank 2,963 allied vessels.
Convoys. Before WW II Britain possessed the world’s largest merchant fleet with 6,700 ocean going vessels. Yet, Britain’s dependence on the goods transported by these ships would pose grave dangers in times of war. Such was the case in World War I, and even more so during World War II. To provide Britain and the continent with food and war materials from Canada and the United States. In 1940 Great Britain alone required imports of 43 million tons, and 38 million tons every year thereafter, so the allies employed the convoy system. In WW II. A typical North Atlantic convoy consisted of 12 to 40 merchant ships, protected by destroyers, frigates, corvettes, and airplanes. There were some 200 different ocean tracks, and 94 of them came under U-boat attack. These routes were named mostly with letters, some also with numerals. The first letter represented the port or country of departure, the second letter the destination. A third letter showed the assigned speed, ‘F’ for fast and ‘S’ for slow. As seen from Britain, ‘H’ meant ‘home’ and ‘O’ stood for ‘outward’. Examples are ‘HX’ (Home from Halifax), ‘ONF’ (Outward for North America Fast) and ‘MKS’ (Mediterranean to UK Slow). The most vital routes were those from the U.S. and Canada to Great Britain and to Murmansk in Russia. Most of the attacks took place her. Often a dozen convoys with more than 20,000 men crossed the Atlantic at the same time, with speeds between seven and nine knots. Bad weather and fog was a blessing for the convoys, as it made U-boat operations very difficult, on the other hand too much smoke from the ships funnels, was a dead giveaway especially on the older coal burning vessels. And a lot of these ships had to slow down and even drop out of the convoys altogether because of this, which left them in greater danger. In perilous waters the convoys sailed in zig-zag patterns to be less vulnerable to attack.
Zig-Zag. Zig-Zagging amounts to the main body of the convoy simultaneously steering predetermined courses for various lengths of time, which would prevent a submarine captain from easily determining the true course of the convoy. Changes in course were made at specific intervals on the clock thus eliminating any visual or electronic signal, which might alert the submarine captain to an impending change. Each convoy has one ship as a Guide-on. That ship is responsible for precise execution of the zig-zag plan and all other ships in the main body must also execute precisely the same zig-zag maneuver to insure maintaining the formation. The Guide-on was generally one of the foremost ships in the main body. Several standard Zig-Zag plans were available for use and they usually were changed daily or as needed.
Escorts. The convoys were defended by destroyers, frigates, corvettes, sloops and cutters, with additional assistance of airplanes and shore based support. One of anti-submarine warfare’s most important tools was the device called “Asdic” used by the Royal Navy, which detected submerged submarines by means of sound wave transmissions. Its range was about 1,400 meters (1,500 yards). Escort vessels surrounding convoys with their Asdic gear provided a protective shield, which U-boats had to penetrate first before being able to fire. Once detected, submarines were pursued by the faster surface vessels and carpeted with depth charges. Later Sonar improvements even detected launched torpedoes and determined a submerged U-boat’s depth. Then came the advent of Radar, and High Frequency Direction Finders (HF/DF) which would pinpoint a U-boat’s position even during very brief radio transmissions.
U-boats. The German U-boat of type VII-a, for example had a speed of 8 knots while submerged and 17 knots on the surface. Length was 66 meters; there were four torpedo tubes in the bows and one in the stern. Armed with 14 torpedoes, their diving range was to a depth of 100 meters. With crews of approx. 50 men, operating range was 6,500 nautical miles at an average speed of 12 knots. Germany was building / commissioning ten boats per month by early 1941, and by 1945 they had built 1,177 of them. By mid 1944 though the days of the U-boats were numbered, and the life expectance of their crews were down to a couple of weeks, the main reasons, new equipment in their detection, and far more accurate weapons that the allies had at their disposal.
Air Cover. During the early years of the war, a large number of convoy battles were fought within the so-called air gap, an area in the North Atlantic beyond the reach of air power. Convoys needed four days steaming to pass through this danger zone. Two major sea battles tell the story: In November of 1942 convoy SC-107 lost 15 vessels with 82,430 tons to a wolf pack of ten U-boats. March of 1943 saw the last great convoy battle when 38 submarines converged on convoys SC-122 and HX-229. Within four days 22 Allied ships were sunk and one fourth of all the mariners on these vessels lost their lives, while the Germans lost just one U-boat in this action. But soon thereafter the tide turned against Nazi Germany.
Liberty Boats. Commencing in 1941, the U.S. undertook a gigantic newbuilding program to produce tremendous numbers of relatively inexpensive ships in record times. 18 new shipyards with altogether 171 slips were created. Based upon the British ‘Ocean class’ design, a simple yet efficient type of freighter came into being, originally called ‘Emergency Ships’. Their drab gray appearance earned them the nickname ‘ugly ducklings’. Then, President Roosevelt proclaimed their purpose as providing Europe with liberty hence their new designation as ‘Liberty Ships’. The very first Liberty ship was SS ‘Patrick Henry’. She was delivered in December of 1941. Building her took 150 days, yet very soon the Americans revolutionized their methods of construction. Most successful were the Kaiser Shipyards of California. For the SS ’Robert E. Peary’, 250,000 components were pre-fabricated at locations across the country. Then, it took just four days, 15 hours, and 29 minutes to join those sections for a completed Liberty ship! This became an absolute record. By 1944, average construction times including individual components took just 42 days. Liberty ships were 441’ long, 57’ wide, of 7,176 gross tons and 10,500 tons deadweight, with five hatches and a speed of 11 knots. Between 1941 and 1945, a total number of 2,751 Liberty ships were completed; their type prefix was ‘EC2’.
Victory Ships. A slightly larger design called ‘Victory Ship’ was built from 1943 onwards, capable of 15 to 17 knot speeds. The first specimen was the SS ‘United Victory’, commissioned in February of 1944. Altogether 541 Victory ships went into service, as type ‘VC2’. Their length was 445’, breadth 62’, with a gross tonnage of 7,607. Just like the Liberty ships, they were armed with bow and stern guns and anti-aircraft cannons, manned by naval personnel. In addition, 550 rapidly constructed T2 and T3 tankers were placed into service. By August of 1942 Allied ship construction fully compensated for their losses. During 1943 American and Canadian shipyards produced 140 freighters per month.
(This glossary compiled by Rhiw.com)
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