Click for larger image

Four days after the Japanese attack at Pearl Harbor on 7 December 1941, Germany declared war on the United States of America. Long before its actual entry into the war, the USA had been participating in the Atlantic campaign on an increasing scale. From 1940 onwards, US naval observers had been attached to the Royal Navy. In mid-September 1941, US ships began to escort convoys between Newfoundland and Iceland. The German Navy had long since identified the western Atlantic as the most vulnerable area for Allied shipping and anticipated rich pickings along the American eastern seaboard.

U-boats were in place to start operations by mid-January 1942. The abundance of targets, including a preponderance of valuable oil tankers sailing between the Caribbean, the Gulf of Mexico and east coast US ports, and the American reluctance to adopt the convoy system created a second "Happy Time" for the U-boat commanders. Between January and June in the North Atlantic, Allied losses reached an average of nearly 88 ships ( 471,948 tons) per month. In May and June alone, U-boats sank over one million tons in US waters. This massive German success was achieved with a relatively small number of boats. However, from mid-March, their operational endurance was boosted by the deployment of submarine tankers (or "milch cows" as the Germans called them) which resulted in strength peaking at 16-18, operating between Nova Scotia and the tip of Florida.

Initially, the Americans preferred to route coastal traffic independently and hunt U-boats by offensive patrols. They had seen the lack of success achieved by the Canadians when escorting slow convoys in autumn 1941. Many US escorts were deployed in the Pacific until the Battle of Midway in early June greatly reduced Japanese naval power. Unfortunately, westbound ships which had been safely convoyed across the Atlantic and eastbound ships loaded with essential supplies in American ports were lost in waters where the existing Allied convoy system could not protect them. Despite pressure from the British, the Americans were slow in adopting suitable defensive measures and did not introduce even a partial convoy system until 1 April.

Gradually, however, an improvement was made in US tactics and began to take effect. Firstly, U-boats were denied their profitable hunting grounds in shallow coastal waters. Then, by the middle of 1942, both north and south bound convoys along the US eastern seaboard were instituted, forcing the U-boats to move from this area to the Caribbean. By September, the US Navy had established a complete interlocking convoy system between Canada and Brazil. Convoys across the Atlantic now took a more direct, southerly route than before to avoid the worst of the northern weather (albeit rendering air cover based on Iceland less effective). Crucially, this was made possible by the introduction to the convoys of tankers, which could refuel escort vessels en route. Other tactical and technical advances were also made. A change in patrol techniques gave convoys better air support. Coastal Command aircraft now had radar and searchlights (known as Leigh lights), which gave them the advantage of surprise over the U-boat, exploited by new, more powerful, depth charges. By August, the arrival of a few Very Long Range Liberators meant that aircraft were beginning to operate in the crucial mid-Atlantic air gap. Shipborne radar and, from July onwards, High Frequency Direction Finding (or "Huff-Duff") equipment, which pinpointed U-boats making radio transmissions on the surface, gave escort vessels a better chance of finding their adversary. Improved training for their commanders and the introduction of standard attack response procedures contributed towards the improved efficiency of convoy escort groups.

Throughout 1942, the numbers of operational U-boats increased rapidly, at a rate significantly faster than the Allies could sink them. In January there were 91, twelve months later the strength had risen to 212; 87 U-boats were lost during the year. Planned wolf pack attacks in the North Atlantic had temporarily ceased in November 1941, though a few isolated assaults were still attempted over the first half of the year. Then, from August, with Western Atlantic and Caribbean waters becoming unprofitable, Admiral Dönitz, the U-boat commander, unleashed his wolf packs in a renewed campaign of increasing intensity against the North Atlantic convoys. He concentrated his forces in the central Atlantic air gap, which all but a few of the covering Allied aircraft could still not yet reach. Dönitz had several advantages. The support of a number of "milch cows" gave the U-boats extended endurance. The Allies were still short of escort vessels. They had also, for most of 1942, lost the ability to read U-boat high-level coded radio signals, whereas German wireless intelligence of Allied convoy movements was still highly successful.

The battle raged for the rest of the year. Between July and December, 480 Allied ships with a tonnage of 2,639,533 tons were sunk in the North Atlantic. The overall, worldwide total for 1942 of nearly 7.8 million tons gave a monthly average not far short of the 700,000 tons Dönitz had identified at the start of the year as that which would soon bring Britain to defeat. His U-boats had accounted for approximately 80% of the sinkings. By the end of 1942, the Admiralty reported that the shipping situation had never been tighter. There were still not enough naval and air escorts and fuel stocks were getting very low. Most of the new merchant shipping being built was American, most of the losses were British. Imports were down one-third on the 1939 total. Paradoxically, the great success of transporting the massive numbers of troops and their supplies needed for the North African landings in November from Britain and the USA had been at the expense of taking the necessary escort ships away from the North Atlantic convoys. For the Allies, the Atlantic battle, on which so much rested, was reaching crisis point.

top