'Paukenschlag' was the German 'second happy time' naval offensive by individual U-boats rather than wolfpacks against Allied shipping off the eastern and south-eastern seaboards of the USA in the Battle of the Atlantic (11 January/7 February 1942).

The 'first happy time' had been the phase of the Battle of the Atlantic during which the U-boats had enjoyed major successes against the British and their allies. This phase had begun in July 1940, almost immediately after the fall of France, which had made possible the basing of U-boats in captured French ports in Brittany and along the coast of the Bay of Biscay, and therefore considerably closer to the British shipping lanes in the Atlantic. When this period ended is a matter of interpretation, but was between October 1940 and April 1941. The primary reason for the German success in this period was the British lack of radar-equipped ships: this meant that the detection of U-boats was very hard as they made surfaced attacks at night. The secondary reason was the British lack of adequate numbers of well-equipped anti-submarine aircraft. Between July 1940 and the end of October in the same year, 282 Allied ships were sunk off the North-Western Approaches to the UK for a loss of 1,489,795 tons of shipping.

The German U-boat crews called the new period the 'second happy time' or the 'golden time' as the USA’s defence measures were signally weak and disorganised, and the U-boats were able to sink a large tonnage of shipping with few losses to themselves: in this period Axis submarines sank 609 ships totalling 3.1 million tons for the loss of only 22 of their own number. This was approximately one quarter of all shipping sunk by U-boats during the World War II, and was by far the most serious defeat ever suffered by the US Navy.

When Adolf Hitler declared war on it on 11 December 1941, the USA became embroiled in a war in which the other Allied combatants had already lost thousands of trained sailors and airmen and were experiencing shortages of ships and aircraft, but was herself at a high state of capability. The US forces lacked the operational experience of the other combatants, however, but the USA was still expanding the strength of its armed forces in terms of numbers and quality of equipment.

The US Navy had been able to learn a considerable amount about modern naval warfare by observing the conflicts in the North Atlantic and the Mediterranean, and through its close relationship with the Royal Navy, and had also gained significant experience in countering the U-boat threat in the Atlantic, particularly after April 1941 when President Franklin D. Roosevelt extended the 'Pan-American Security Zone' eastward almost as far as Iceland. The USA possessed a huge manufacturing capability, including the largest and possibly the most advanced electronics industry in the world. Finally, the USA had a favourable geographical position from a defensive aspect: New York, for example, is some 3,000 miles (4825 km) to the west of the ports in the Brittany area of German-occupied France which were then used extensively by the U-boats.

Even so, Vizeadmiral (from 14 March 1942 Admiral) Karl Dönitz, commanding the German navy’s U-boat arm, perceived the US entry into the war as a great opportunity to decimate the Allies' merchant ship tonnage. The German navy no longer had surface tankers in the North Atlantic to refuel its U-boats, for these had been lost after 'Ultra' intelligence revealed their operating locations, and the standard 'Type VII' class U-boat had insufficient range to patrol off the coast of North America, so the only weapons Dönitz had were the larger 'Type IXC' class boats. These were less agile and submerged more slowly than the smaller 'Type VII' class boats, and were therefore more vulnerable. They were also fewer in number than the older and more easily built 'Type VII' class boats.

Immediately after the German declaration of war on the USA, Dönitz began to implement 'Paukenschlag', demanding that 12 'Type IXC' boats be made available. However, at the urging of Adolf Hitler, the naval staff demanded that six of the boats be retained in the Mediterranean and/or each side of the Strait of Gibraltar, where in fact they could achieve little, and then one of six boats committed to 'Paukenschlag' developed mechanical problems. This left just five long-range boats for the opening moves of the campaign. Having taken on all the fuel, ammunition and food it could, the first 'Type IXC' class boat departed Lorient on the west coast of France during 18 December 1941 to reach the east coast of the USA on 13 January, two days before the other four boats departed Brest and Lorient. Each boat carried sealed orders to be opened after passing 20° W, and directing them to different parts of the North American coast. No charts or sailing directions were available: Kapitänleutnant Reinhard Hardegen of U-123, for example, was provided with two tourist guides to New York, one of which contained a fold-out map of the harbour. Each U-boat made routine signals on exiting the Bay of Biscay, which were picked up by the British Y service and plotted at the Submarine Tracking Room in London, allowing the British to follow the progress of the 'Type IXC' class boats across the Atlantic, and cable an early warning to the Royal Canadian Navy. Working on the slimmest of evidence, Roger Winn of the Submarine Tracking Room correctly deduced the target area and passed a detailed warning across the Atlantic to Admiral Ernest J. King, the Commander-in-Chief, US Fleet and, from 18 March, Chief of Naval Operations, of a 'heavy concentration of U-boats off the North American seaboard', including the five boats already on station and more boats in transit for a total of 21 boats.

Rear Admiral Frank T. Leighton of the US Combined Operations and Intelligence Center then informed the responsible area commanders, but little or nothing else was done. The German captains' primary target area was the 'North Atlantic Coastal Frontier', commanded by Rear Admiral (from March 1942 Vice Admiral) Adolphus Andrews and covering the area from Maine to North Carolina. Andrews had practically no modern forces: on the water he commanded seven US Coast Guard cutters, four converted yachts, three 1919-vintage patrol boats, two gunboats dating to 1905, and four wooden submarine chasers. He could also call on about 100 aircraft, but these were short-range types suitable only for training. As a result of the traditionally antagonistic relationship between the US Navy and the USAAF, all larger aircraft remained under USAAF control, and in any case the USAAF had neither the training nor the equipment for anti-submarine work.

Even so, there was much which could have been achieved: the lessons of the campaign against the U-boat during World War I were plain, and British experience in the first two years of World War II had confirmed them. Ships sailing in convoy, with or without escort, were far safer than ships sailing alone; standard routings should be avoided wherever possible; navigational markers, lighthouses, and other aids which an enemy might exploit should be removed; and a strict black-out should be enforced. None of these measures was even attempted. Coastal shipping continued to sail along marked routes and burn normal steaming lights. On 12 January, Andrews was warned that three or four U-boats were about to start operations against shipping in US coastal waters, but refused to institute a convoy system on the grounds that this would only provide the U-boats with a greater concentration of targets.

For the five 'Type IXC' class boats in the first wave of 'Paukenschlag', the result was a plethora of targets. The boats cruised along the coast, safely submerged through the day and surfacing at night, to pick off merchant vessels outlined against the lights of cities and amusement parks. Hardegen’s U-123 sank seven ships totalling 46,744 tons before running out of torpedoes and turning for home, Kapitänleutnant Ernst Kals in U-130 despatched six ships of 36,988 tons, Kapitänleutnant Richard Zapp in U-66 five ships of 33,456 tons, and Kapitänleutnant Heinrich Bleichrodt in U-109 four ships of 27,651 tons. U-125 under Kapitänleutnant Ulrich Folkers, a new captain on his first cruise, sank only a single 6,666-ton vessel.

Despite the urgent need for action, little was done to try to stop the sinkings. The US Navy was desperately short of anti-submarine vessels, partly because of Roosevelt’s 1941 decision to loan 50 obsolete World War I destroyers to the UK in exchange for 99-year leases on foreign bases, partly because the massive new naval construction programme had allocated priority to other types, and partly because the destroyers which remained available were assigned to trans-Atlantic convoy escort and therefore did not come under Andrews’s command. There were no fewer than 25 of the destroyers in the Atlantic Convoy Escort Command on the US east coast at the time of the first attacks, including seven at anchor in New York harbour, yet when U-123 sank the 9,500-ton Norwegian tanker Norness within sight of Long Island in the early hours of 14 January none of these ships was dispatched to investigate, with the result that U-123 was free to sink the 6,700-ton British tanker Coimbra off Sandy Hook on the following night before proceeding to the south toward New Jersey. By this time there were 13 destroyers idle in New York harbour, yet still none was employed to deal with the immediate threat, and over the following nights U-123 was offered and happily accepted a succession of easy targets, most of them burning navigation lights.

When the U-boats of the first wave returned to port in France during the early part of February, Dönitz wrote that each of his commanders 'had such an abundance of opportunities for attack that he could not by any means utilise them all: there were times when there were up to 10 ships in sight, sailing with all lights burning on peacetime courses.'

During March the UK transferred some 50 anti-submarine trawlers and 10 corvettes for the defence of the USA’s east coast, and also allocated No. 53 Squadron of RAF Coastal Command to Rhode Island to help in the protection of New York harbour. Other British warships assumed escort duties in the Caribbean Sea and on the vital route plied by oil tankers between Aruba in the Dutch West Indies and New York.

A significant failure in US planning before the war was the lack any perception that specialised ships would be required for the convoy escort role: such escort vessels needed to possess only a modest speed but had to be able to carry large numbers of depth charges, to be highly manoeuvrable, and to be able to remain on station for long periods, whereas the type of fleet destroyer on which the US Navy had concentrated its efforts were equipped for high speed and offensive action, and was far from ideal for this type of work. There was no equivalent of the Royal Navy’s 'Black Swan' class of sloops in the US inventory when the war started.

By this time, the second wave of 'Type IXC' class boats had arrived in US waters, and the third wave had reached its patrol area off the oil ports of the Caribbean Sea. With easy pickings available and all 'Type IXC' class boats already committed, from February Dönitz allowed the shorter-range 'Type VIIC' class boats to take a hand. This required extraordinary measures: every conceivable space was crammed with provisions, some of the fresh water tanks were filled with Diesel oil, and the Atlantic was crossed at very low speed on a single engine to conserve fuel. This effort was greatly aided by the availability of a few 'Type XIV' class 'milch cow' boats, which were able to ferry over the Atlantic fuel and other supplies sufficient for about a dozen attack boats, allowing Dönitz to keep some 27 U-boats operational between Nova Scotia and British Guiana.

In the USA there was still no concerted response to the attacks. Overall responsibility rested with King, but he was more concerned with the Pacific theatre or, as his critics put it, was obsessed with the Pacific. Andrewss North Atlantic Coastal Frontier was expanded to take in South Carolina and renamed the Eastern Sea Frontier, but most of the ships and aircraft which were required nonetheless remained under the command of Admiral Royal E. Ingersoll, commanding the Atlantic Fleet, who was often at sea and unavailable to make decisions.

Wynns detailed weekly U-boat situation reports from the Submarine Tracking Room in London were available, but were steadfastly ignored. Inevitably, the US Navy confidently announced that many of the U-boats would never enjoy the return portion of their voyage but that details of U-boat sinkings could not be released lest the information aid the Germans. Thus through 1942s summer and the first half of its autumn there were no sinkings of U-boats and, just as astonishingly, still no attempt to organise convoys and still no black-out of coastal towns to make ships more difficult to see.

In this 'second happy time', therefore, the U-boats sank some 455 ships, including many vital tankers, while operating up to 300 miles (485 km) off the US eastern seaboard: these sinkings totalled some 196,243 tons in January, 286,613 tons in February, 354,489 tons in March, 276,131 tons in April, 451,991 tons in May, and 416,843 tons in June. Losses of U-boats in the Atlantic and Caribbean during the same months were one, two, three, two, one and two respectively.

However, in April 1942 the USA did finally start a limited convoy system, extended in May to nonstop convoys between Halifax and Key West, and together with increasing anti-submarine capability and skill, this began to trim away the advantages which the U-boats had enjoyed up to this time. These were already under threat at home by Hitler, who was unwilling that boats be despatched to the other side of the Atlantic at a time he felt the Mediterranean and Norway were, he believed, the 'zones of destiny'. Thus Grossadmiral Erich Raeder, commander-in-chief of the German navy, did not demur when Hitler insisted that of the 41 new U-boats delivered in the first half of 1942, 26 should be used off Norway and another two in the Mediterranean, leaving only 13 to replace the total of 13 boats Dönitz had lost in the Atlantic. From June, therefore, Dönitz called his singleton boats out of US coastal waters to re-form the 'wolfpacks' of the central Atlantic, and 'Paukenschlag' was over, defeated as much by Hitler and Raeder as by the Americans.

The belated US effort to defeat 'Paukenschlag' was marked by the declining rate of Allied merchant shipping losses in the area of Andrews’s Eastern Sea Frontier, between Newfoundland in the north and Florida in the south: whereas 128 ships had had been sunk in the first quarter of 1942, only 21 succumbed in the year’s second quarter, and none at all in each of the two last quarters.

The 'second happy time' for the U-boat commanders did not end with the introduction of convoys in the Eastern Sea Frontier area, though. By a time late in April 1942 Dönitz had put together a force of 18 U-boats for a major effort against independently sailing ships in the waters off Florida, and another nine 'Type IX' class U-boats were deployed to the Caribbean to hunt in the waters between the Bahamas and Trinidad. Moreover, the U-boat arm now possessed the means to nourish the cross-Atlantic campaign by sending the first of the 1,660-ton 'Type XIV' 'milch cow' U-boats across the Atlantic: each of these boats could deliver 425 tons of fuel, four torpedoes, fresh food and vital spare parts (they also had provision for the baking of fresh bread), and their availability made it possible to keep 10 or more U-boats operating deep in the Caribbean. The first refuelling took place on 22 April when the first 'Type XIV' boat, Kapitänleutnant Georg von Wilamowitz-Moellendorff’s U-459 made rendezvous with Korvettenkapitän Klaus Scholtz’s U-108 some 500 miles (6800 km) to the north-east of Bermuda. Within two weeks U-459 had topped up the tanks of 12 medium-size 'Type VII' boats and two larger 'Type IX' boats. Two more 'milch cow' boats were then dispatched to enable the offensive to be carried right across the Gulf of Mexico as far as the Panama Canal.

For Vice Admiral John H. Hoover, commanding the Caribbean Sea Frontier area from a headquarters at San Juan, Puerto Rico, May and June 1942 were appalling months as sinkings in this area rose to 148. In addition to long-range attacks into the Gulf of Mexico, Dönitz ordered his commanders to make for the ports of the Mississippi river delta, most notably New Orleans and Mobile, in the area of Captain Russell S. Crenshaw’s (from 3 June Rear Admiral James L. Kauffman’s) Key West- but later Miami-based Gulf Sea Frontier, where there was a 'target-rich environment' of tankers and bauxite carriers supplying the USA greatest concentration of refineries and aluminium smelting facilities.

The new part of the German offensive was designed to disrupt these industries, which were crucial to the whole of the US war effort. On 6 May 1942 Korvettenkapitän Harro Schacht’s U-507 began the offensive by sinking the 6,759-ton US bauxite carrier Alcoa Puritan some 100 miles (160 km) to the south of Mobile, Alabama. On the same day the Gulf of Mexico was declared a danger zone in which there were to be no unescorted sailings, but the Gulf Sea Frontier headquarters, still located in Key West, lacked the resources to implement this decision as it had only two destroyers, a limited miscellany of smaller craft and about 20 aircraft with which to provide escort for all the shipping in the area.

U-507 was soon joined by Kapitänleutnant Erich Würdemann’s U-506, and the two boats were soon sinking a ship per day. The number of U-boats operating in the Gulf of Mexico never exceeded six, but these sank 41 ships, whose 220,000 tons were double those of any month on the Eastern Sea Frontier, and more importantly more than half of the tonnage comprised tankers.

As the immediate aftermath of 'Paukenschlag' proper continued in the USA’s southern waters, General George C. Marshall, the US Army chief-of-staff, on 19 June 1942 criticised the US Navy’s performance in a letter to King. The latter responded in a letter citing the service’s shortage of escort vessels and submarine chasers, which had compelled the US Navy to 'improvise rapidly and on a large scale'. Only recently, he added, had the Eastern Sea Frontier achieved the strength to allow the institution of the convoy system which since 15 May had made the waters of the US eastern seaboard comparatively safe. King added the hope that the loss rate outside the Eastern Sea Frontier’s area of responsibility would be reduced as air cover became available, and ended with the statement that revealed his altogether belated adoption of the convoy system: 'I might say in this connection that escort is not just one way of handling the submarine menace; it is the only way that gives any promise of success. The so-called patrol and hunting operations have time and again proved futile.' What King did not address is why it had taken him six months to reach this conclusion, a period in which U-boats had been able to sink more than 1 million tons of shipping. It was only on 10 June that King finally accepted the need for a full convoy system throughout the Caribbean with the aid of British escort groups withdrawn from the Atlantic and a squadron of RAF Coastal Command Lockheed Hudson anti-submarine aircraft to operate from Trinidad.

Late in the summer of 1942, the U-boat offensive off the east and south coasts of the USA finally began to lose their advantage as escorted convoys grew more numerous and anti-submarine patrols took a greater toll of the U-boats.

Meanwhile the southern shift of a major part of the U-boat effort to the waters off Trinidad in July and August was endangering the heavy coastal traffic sailing along the Brazilian coast. This threat to vital mineral supplies persuaded the USA to seek and receive Brazilian permission to dispatch US Marine forces to establish a series of airstrips on the largely undefended 4,000-mile stretch of (6440-km) coast on which, the USA feared, the Germans might build secret supply bases in isolated coves to support the U-boat offensive on the mid-Atlantic. Hitler had already offered the Brazilian government millions of captured US dollars in return for their co-operation, but the Brazilian authorities had swiftly seized all the Axis sympathisers in their country.

Spurred by this fact as much as by strategic considerations, Hitler in June agreed to Raeder’s the proposal to extend the U-boat operations to the coast of Brazil. This was a major error as, after five Brazilian merchant vessels had been sunk in three days, Brazil declared war on Germany and Italy on 22 August, and this opened the way for Vice Admiral Jonas H. Ingram’s South Atlantic Force quickly to move into the Brazilian bases from which its ships and aircraft could control the important mid-Atlantic narrows.

The establishment of US Navy protection of the coastal shipping off South America was the final link in the creation of a comprehensive Allied convoy network. The Interlocking System, as this network came to be known, was operating at a very high level of efficiency by the autumn of 1942. All northbound convoys were scheduled on five-day cycles to connect with the departure of the transatlantic 'main line' from Halifax, Nova Scotia. This divided at New York, with one main line extending to Key West and the other to Guantánamo, Cuba. From Key West, a 10-day cycle served Galveston and the Mississippi river ports, and from Guantánamo the convoys ran across the Caribbean to Panama, Venezuela and Curaçao, then to the south along the Brazilian coast. Thus August 1942 marked the end of the 'second happy time': during the three months which followed, some 1,400 ships were convoyed through the Interlocking System and only 11 of these were sunk.