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A U-boat shelling a merchant ship which had remained afloat after being torpedoed

The early phase of the Battle of the Atlantic during which Kriegsmarine U-boats enjoyed significant success against Allied warships and merchantmen was referred to by U-boat crews as the Happy Time (German: Die glückliche Zeit),[1] and later the First Happy Time, after a second successful period was encountered.

It started in July 1940, almost immediately after the Fall of France, which brought the German U-boat fleet closer to the British shipping lanes in the Atlantic. From July 1940 to the end of October, 282 Allied ships were sunk off the north-west approaches to Ireland for a loss of 1,489,795 GRT of merchant shipping.[2]

The reason for this successful Axis period was the British lack of radar and huff-duff-equipped ships which meant that the U-boats were very hard to detect when they made nighttime surface attacks – ASDIC (sonar) could only detect submerged U-boats.

When it ended is a matter of interpretation, with some sources claiming October 1940[3] and others extending it to April 1941,[4] after the Germans lost three prominent U-boat commanders: Günther Prien, Joachim Schepke, and Otto Kretschmer.[5]

See also

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References

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First Happy Time

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The First Happy Time was a highly successful phase for German operations during the in , spanning from July to October 1940, during which sank 282 Allied merchant ships totaling 1,489,795 gross register tons, primarily off the British coast and in the western Atlantic approaches. This period marked a turning point following the fall of in June 1940, which allowed Admiral to base his submarines in Atlantic ports like Brest and , drastically reducing transit times and enabling more aggressive patrols. The success stemmed from the introduction of wolfpack tactics, where coordinated groups of ambushed poorly defended convoys, as exemplified by devastating attacks on (losing 20 of 35 ships from 16 to 19 October) and Convoy HX 79 (12 of 49 ships sunk on 20 October). Italian submarines also contributed from bases in , adding to the pressure on British shipping lanes. These losses exacerbated Britain's supply shortages, threatening its war effort, but prompted Allied improvements in convoy escorts, air cover, and that curtailed effectiveness by early 1941. The term "Happy Time" reflected the low risk to , with only six losses during this period, contrasting sharply with later phases of the campaign.

Background

Early U-boat Campaign (1939–June 1940)

Upon the outbreak of , declared on September 3, 1939, authorizing U-boats to attack merchant shipping without warning. The first such action occurred that day when U-30 torpedoed and sank the British passenger liner Athenia approximately 250 miles northwest of , resulting in 112 deaths among her 1,418 passengers and crew. This incident marked the beginning of the and heightened tensions, though the German high command initially denied responsibility to avoid escalating U.S. involvement. At the war's start, the had approximately 57 U-boats capable of operational deployment, with only about half immediately available for frontline service due to training and maintenance needs. Early successes were limited but notable; in the first week of the campaign, U-boats sank ships totaling around 65,000 gross register tons (GRT), followed by 46,000 GRT in the second week and 21,000 GRT in the third. By the end of , the tally reached 50 merchant vessels sunk, amounting to 200,728 GRT, though these figures represented a modest strategic impact on Allied shipping overall. The British response included the rapid adoption of a system, with the first outbound OB-1 departing on 7 , and further implementation in October, which significantly reduced vulnerability by concentrating under escort protection. Operational constraints severely hampered U-boat effectiveness during this period. Based primarily in German ports on the , such as and , U-boats faced lengthy transit times—often up to two weeks—to reach patrol areas in the , exposing them to detection and attack by the Royal Air Force and during the vulnerable surfaced phases. , appointed commander of U-boats (Befehlshaber der Unterseeboote) in January 1939, repeatedly advocated for a larger fleet of at least 300 submarines to saturate routes and overwhelm defenses, drawing from his experiences. He also promoted the concept of Rudeltaktik (wolfpack tactics), involving coordinated group attacks on s, but these were not yet feasible due to insufficient numbers, limited radio communication capabilities, and the ongoing "Phoney War" dynamics that restricted aggressive operations. A rare bold exploit that boosted German morale occurred on October 14, 1939, when U-47, commanded by Korvettenkapitän , penetrated the heavily defended British naval base at in the Islands. Despite incomplete blockships and lapsed antisubmarine measures, Prien navigated treacherous channels under cover of darkness and fired three torpedoes at 1:16 a.m., striking the battleship . The ship capsized and sank within 13 minutes, claiming 835 lives from her crew of 1,208 and marking the first capital ship loss for the Royal Navy in the war. Prien's return to was celebrated as a victory, earning him the Knight's Cross of the [Iron Cross](/page/Iron Cross), though it prompted the British to reinforce 's defenses. These early operations demonstrated the potential of U-boat warfare but underscored its limitations until strategic shifts, such as the fall of in , which allowed basing on the Atlantic coast and shortened transit routes.

Fall of France and Strategic Opportunities

The marked the capitulation of to following the rapid German invasion that began on 10 May, enabling the occupation of strategic Atlantic coastline territories. German forces swiftly secured key ports including Brest on 19 June and on 18 June, transforming these facilities into forward bases for operations. This occupation extended to other sites such as St. Nazaire, La Pallice, and , providing direct access to the open Atlantic without the need to navigate the hazardous British-controlled waters around the . The relocation to French ports drastically shortened U-boat transit times to the primary hunting grounds in the , reducing the journey from German home bases—previously taking 4 to 6 days—from or to mere hours from Brest or , thereby adding up to 10 extra days per patrol for combat operations. The first U-boat to utilize these facilities, U-30, arrived in on 7 July 1940, followed by a steady influx that saw 25 Type VII submarines based in the French ports by August 1940. Admiral , as (BdU), capitalized on this by relocating his headquarters from to a requisitioned villa in the Kernevel neighborhood near on 16 October 1940, facilitating closer coordination with the expanding submarine fleet. This repositioning represented a pivotal strategic shift, placing U-boats immediately adjacent to Britain's critical import convoys in the and minimizing exposure to early Allied detection during transit. No longer constrained by the logistical limitations of the pre-June period—when operations from German ports yielded modest sinkings of around 1.5 million tons over nine months—these bases ended the tentative "phony war" phase of U-boat warfare and positioned to intensify pressure on Allied shipping lanes.

Course of the Campaign

July to September 1940 Operations

The opening phase of the First Happy Time saw a marked increase in effectiveness in the , where German submarines exploited vulnerabilities in Allied shipping routes following the Fall of . From July to September 1940, U-boats sank 155 Allied merchant vessels totaling approximately 776,000 GRT, averaging over 50 ships per month—a surge from the pre-1940 baseline of fewer than 20 monthly sinkings. This period marked the initial high sinkings, driven by the redeployment of French Atlantic bases that extended U-boat operational range and reduced transit times. Key operations highlighted the growing prowess of individual U-boat commanders, with coordinated patrols emerging as a tactical innovation, though full wolfpack formations were not yet employed. For instance, U-99 under Korvettenkapitän Otto Kretschmer conducted a highly successful from 14 July to 31 August 1940, sinking seven for a total of 27,631 GRT. In late August, U-boats including U-37, U-28, and U-101 attacked Convoy SC-1 in the North Atlantic, resulting in the sinking of four totaling 10,633 GRT. These actions demonstrated early use of radio-directed targeting, where U-boats shared sightings to concentrate on convoys without effective Allied interception of their communications. Several factors contributed to this surge in successes, including a scarcity of Allied escorts strained by recovery from the and preparations against a potential German of Britain. The prioritized coastal defenses and had limited destroyers and corvettes available for mid-ocean convoy protection, leaving many shipments with minimal or no escort. U-boats operated with relative impunity in these gaps, focusing on unescorted or lightly protected traffic in the , which accounted for the majority of losses during these months.

October to December 1940 Escalation

The escalation of the from October to December 1940 marked the peak of the First Happy Time, as German forces capitalized on expanded operations in the North Atlantic following the initial successes of the preceding months. Building on the 155 ships sunk between and , the deployed larger numbers of submarines to target vulnerable convoys, achieving record monthly sinkings despite increasingly harsh weather conditions. By October, approximately 21 U-boats were operational in the Atlantic, allowing for coordinated wolfpack tactics that overwhelmed Allied escorts. Italian submarines, based in , contributed additional sinkings during this period. October 1940 saw the highest intensity of attacks, with U-boats sinking 60 merchant vessels totaling 342,204 gross register tons (GRT), contributing to a cumulative total of 215 ships and over 1.1 million GRT lost from July through October by German U-boats alone (overall Axis total 282 ships and 1.49 million GRT including Italian submarines). A pivotal event was the assault on HX-79 on the night of October 19–20, where five U-boats, including U-38 under Heinrich Liebe, sank 12 ships for 75,069 GRT in a single engagement about 120 miles west-southwest of . This action exemplified the vulnerability of fast convoys from Halifax, as poor visibility and limited escorts enabled the submarines to maneuver undetected and fire multiple salvos. Heavy autumn gales further complicated Allied defenses, scattering ships and reducing visibility, yet the U-boats maintained a high success rate, losing only one boat for every roughly 50 merchant vessels sunk during the month. November and December sustained the momentum, though with varying intensity amid worsening storms that occasionally hampered torpedo launches and surfacing operations. In November, U-100 under Joachim Schepke achieved a standout performance, sinking seven ships totaling 24,601 GRT on alone during attacks on Convoy SC-11, showcasing the effectiveness of Type VIIB boats in night surface actions. Overall, 33 ships were sunk that month, followed by 41 in December, as U-boats shifted focus to slower convoys like OB and HX series, exploiting gaps in escort coverage. These operations inflicted severe pressure on Allied shipping routes, with minimal German losses—only a handful of U-boats sunk across the quarter—underscoring the campaign's one-sided nature at its height.

January to March 1941 Decline

During the first quarter of 1941, German U-boats sank 99 Allied totaling approximately 545,782 gross register tons (GRT), with monthly rates averaging around 33 vessels: 15 ships (99,050 GRT) in , 44 ships (211,885 GRT) in , and 40 ships (234,847 GRT) in March. This marked a decline from the peak of the First Happy Time in October 1940, when U-boats achieved higher per-patrol success rates against less protected targets. A notable engagement occurred with HX-106 in mid-February 1941, when U-96, commanded by , attacked the 41-ship convoy en route from Halifax to , sinking two vessels (18,503 GRT total) and damaging one (10,516 GRT) on 13 February despite the presence of escorting warships. Earlier on 8 February, the convoy had been sighted by the German battleships Scharnhorst and Gneisenau, but the surface raiders withdrew without engaging due to the risk of alerting British forces, resulting in only partial success for the Axis attackers overall. The period saw five U-boats lost in March alone—U-47 (missing, presumed mined), U-70 (depth-charged by HMS Kingston and HMS Wolverine), U-99 (depth-charged by HMS Walker), U-100 (depth-charged by HMS Vanoc), and U-551 (depth-charged by HMS Aberdeen)—with no losses in or , bringing the quarterly total to five. These casualties contributed to a noticeable decrease in sinkings per , as operational boats faced growing challenges in locating and engaging targets effectively. Several factors eroded U-boat effectiveness during these months, including a shift toward more organized Allied convoys, which reduced the number of independent merchant sailings vulnerable to opportunistic attacks. Additionally, some were diverted to Norwegian waters to support defensive operations against British commando raids, such as the 4 March assault on the Islands (), thereby limiting their availability for Atlantic patrols.

Tactics and Technology

German U-boat Methods

During the First Happy Time, German s primarily employed nighttime surface attacks to maximize their effectiveness against Allied convoys, approaching from the dark side to targets against the moonlit sky while using high-speed runs to penetrate escort screens. These operations allowed U-boats to achieve speeds of up to 17.7 knots on the surface, enabling rapid launches from all forward tubes before firing stern torpedoes or escaping into the wakes of merchant vessels. Deck guns, typically an 88 mm gun with 220 rounds, were often used to finish off damaged or smaller ships after strikes, conserving precious ammunition. To minimize detection risks, U-boats avoided submerging during daylight hours, reserving dives for evasion after attacks, as surface transit conserved battery power and exploited the limitations of Allied ASDIC, which was ineffective against surfaced vessels. U-boat coordination during this period relied on individual "lone wolf" patrols, where submarines operated independently but reported sightings via radio to Befehlshaber der U-Boote (BdU) headquarters for dynamic tasking. The first U-boat to detect a convoy would act as a "shadower," transmitting its position, course, and speed to BdU, which then directed nearby boats to converge for coordinated strikes, laying the groundwork for later wolfpack tactics. Shared sightings through these radio reports allowed informal groups of U-boats to form ad-hoc attacks, particularly in June 1940 when initial wolfpack trials began under tactical control by senior officers, though structured packs were not yet standard. This system, influenced by Admiral Karl Dönitz's World War I experiences, emphasized aggressive opportunism over rigid formations early in the campaign. The workhorse of the U-boat fleet, the Type VIIC submarine, carried 14 torpedoes—loaded in four bow tubes and one stern tube—with a surfaced range of 8,500 nautical miles at 10 knots, enabling extended patrols into the Atlantic shipping lanes. Torpedoes were equipped with magnetic pistols designed to detonate under a ship's hull for maximum damage, but these suffered significant reliability issues in 1940, including premature explosions due to magnetic interference and depth-keeping failures where warheads ran deeper than set. Such malfunctions, evident in operations like the invasion of where 30-35% of attacks failed, forced commanders to rely more on contact pistols or deck guns and contributed to early frustrations despite overall successes. Although prototypes of the Schnorchel—a retractable tube for running diesels while submerged—were tested on captured Dutch submarines in 1941 after their acquisition in 1940, the device saw no widespread adoption during the First Happy Time due to initial skepticism and prioritization of other technologies. These early experiments, focused on ventilation rather than full propulsion, did not progress to operational use until 1943, leaving U-boats dependent on surface diesel running for endurance.

Allied Countermeasure Shortcomings

The primary technological limitation of Allied during the First Happy Time was the ASDIC sonar system, which was effective only for detecting submerged U-boats at ranges of approximately 0.5 to 0.75 miles but proved useless against surfaced attacks, particularly those conducted at night when U-boats could approach undetected. Ambient noise from merchant ships further disrupted ASDIC signals, reducing its reliability in group formations and allowing U-boats to evade detection during wolfpack assaults. This shortfall was exacerbated by the system's inability to determine target depth accurately or operate effectively in rough seas, leaving escorts vulnerable to the U-boats' preferred surface tactics. A critical equipment deficiency was the absence of widespread and (HF/DF, or "Huff-Duff") on escort vessels until mid-1941, with most and U.S. Navy ships lacking these tools for detecting surfaced s beyond visual range or triangulating radio transmissions from over the horizon. Centimetric , which later revolutionized night detection, was not deployed on escorts during this period, and initial technical exchanges between the U.S. and Britain on direction-finding equipment did not yield operational installations until September 1941. Air cover for convoys was similarly inadequate due to limited long-range aircraft availability, leaving the mid-Atlantic "air gap" exposed to operations. Organizational challenges compounded these issues, as the Royal prioritized home waters defense following the in May-June 1940, where six destroyers were sunk and 23 damaged, severely depleting forces. The U.S. , entering convoy duties in September 1941, lacked a standardized anti-submarine until June of that year, resulting in uncoordinated tactics and insufficient for Atlantic operations. Although the transferred 50 aging U.S. destroyers to Britain in September 1940, many required extensive refits, leaving HX and SC series—such as HX.79 in October 1940 and SC 7 in October 1940—poorly protected with as few as four escorts for dozens of , leading to heavy losses like 16 vessels in SC 7. Early trials of the Leigh Light-equipped aircraft in 1941 aimed to counter night surface attacks by illuminating U-boats for visual strikes, but these were initially ineffective due to the light's integration with ASV Mk.II radar, which had a minimum detection range too long for coordinated attacks, delaying its operational impact until later refinements.

Impact and Losses

Allied Merchant Shipping Sunk

During the First Happy Time, from July to October 1940, German U-boats sank a total of 282 Allied merchant ships, amounting to 1,489,795 gross register tons (GRT) of shipping. This period marked a devastating phase for Allied maritime supply lines, with sinkings concentrated in the Atlantic approaches to Britain. The peak occurred in October 1940, when U-boats accounted for 60 vessels totaling 342,204 GRT. Losses were predominantly among vital supply vessels, with roughly 70% consisting of tankers and cargo carriers that carried essential fuel, food, and raw materials. A notable example was SC-2 in 1940, which lost 5 ships totaling 20,943 GRT to coordinated attacks. These strikes highlighted the vulnerability of outbound and inbound convoys in the early stages of the campaign. The economic ramifications were profound, as the sinkings disrupted roughly 15% of Britain's critical imports during peak months, exacerbating shortages of food and fuel that threatened civilian morale and industrial output. Marine war risk insurance rates for Atlantic voyages surged dramatically, often exceeding 10% of a ship's value by late 1940, deterring neutral shipping and further straining Allied . Geographically, about 80% of these losses occurred in the off , where exploited gaps in Allied air cover and escort protection to ambush convoys close to British ports. This focus amplified the psychological and strategic pressure on the Royal , forcing reallocations of resources to defend the chokepoint. The high success ratio—approximately 56 ships sunk for every lost in the period—underscored the imbalance until Allied countermeasures gained traction.

German U-boat Casualties

During the First Happy Time, from July to October 1940, German losses remained comparatively low, with a total of five submarines sunk in against Allied forces in the North Atlantic, representing less than 20% of the approximately 25-30 operational s deployed but underscoring the minimal risk to the wolfpack tactics employed. These losses were overshadowed by the sinking of 282 Allied merchant vessels in the same period, yielding a success ratio of approximately 56 ships per lost. Personnel casualties were severe for the affected crews, totaling around 240 killed, as each Type VII typically carried 40–50 men, with most sinkings resulting in near-total loss of life. The primary causes of these sinkings were depth-charge attacks by escorting destroyers and sloops during defenses, which forced submarines to the surface where they could be rammed or finished off with gunfire. Minefields laid by Allied forces accounted for some earlier losses, such as U-25 in August 1940 off , while only one sinking—U-26 on July 1, 1940, southwest of —was attributed to combined and action. This predominance of surface vessel engagements highlighted the vulnerabilities exposed when operated aggressively near , though overall attrition remained low enough to sustain morale and operations.

Aftermath

Immediate Consequences

In response to the mounting losses during the First Happy Time, issued the "" directive on March 6, 1941, designating the defense of maritime supply lines as the overriding priority for Britain's war effort and calling for the coordination of all available resources to protect convoys. This directive emphasized the urgent need to counter the threat, leading to the establishment of the Committee to oversee antisubmarine measures and convoy protections. Concurrently, the accelerated its support under the Act, enacted on March 11, 1941, which included provisions for transferring antisubmarine escorts and other naval assets to Britain to bolster convoy defenses in the North Atlantic. On the Allied side, the period's end prompted a surge in initiatives to offset sunk , exemplified by President Franklin D. Roosevelt's announcement on January 3, 1941, of a $350 million emergency program that laid the groundwork for the of Liberty ships, with the first vessels launched in September 1941. These efforts were critical as British imports had declined to approximately 62% of prewar levels by 1941, from an average of over 50 million deadweight tons annually to 31 million, straining food and supplies and necessitating widespread , including petrol restrictions imposed since September 1939 and extended to essential civilian use by early 1941. Fuel rationing, in particular, limited private motoring and prioritized military and industrial needs, reflecting the acute resource pressures from disrupted Atlantic trade routes. From the German perspective, the successes of the First Happy Time provided a significant morale boost to the , validating the arm's effectiveness and encouraging further investment in , though Admiral continued to advocate for a fleet expansion to 300 operational to sustain pressure on Allied shipping. However, the immediate aftermath saw a tactical pivot, with several redirected to the Mediterranean theater starting in early 1941 to support operations against British forces there, temporarily reducing Atlantic deployments. Sinkings in 1941 reflected this decline, with accounting for 234,847 tons of Allied shipping—down from peaks exceeding 300,000 tons in late 1940—marking a 50% drop from the monthly average during the height of the campaign. The sinking of U-47 (, presumed lost with all hands), U-100 (, killed), and the capture of U-99 () in 1941 further underscored this turning point for German operations.

Broader Role in the Battle of the Atlantic

The First Happy Time represented a pivotal contribution to the German strategy in the , accounting for approximately 20% of total Allied merchant shipping losses between 1940 and 1941 through the sinking of over 1.4 million gross register tons in just four months. This period underscored the 's potential as a decisive weapon, as unrestricted operations following the Fall of allowed German submarines to target vital supply lines with minimal interference, sinking hundreds of vessels and disrupting Britain's economic lifeline. The success validated Admiral Karl Dönitz's emphasis on prioritizing merchant tonnage over direct naval engagements, reinforcing his advocacy for mass production to achieve strategic strangulation of Allied imports. The campaign's outcomes prompted critical Allied adaptations, accelerating investments in radar technology, enhanced air cover for convoys, and intensified codebreaking efforts against the to counter threats. These responses addressed the vulnerabilities exposed during the Happy Time, such as inadequate escort protection and limited aerial surveillance, ultimately shifting the balance toward more effective . Historically, the First Happy Time marked a transition from a largely defensive U-boat posture—constrained by bases in Germany and early wartime restrictions—to an aggressive offensive phase, enabling wolfpack tactics in open Atlantic waters. This era of dominance contrasted sharply with the U-boat arm's catastrophic defeats in Black May 1943, when Allied technological and tactical superiority led to the loss of 41 submarines in a single month, highlighting the temporary nature of early German gains.

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