Black May: The Epic Story of the Allies' Defeat of the German U-Boats in May 1943

by Michael Gannon

In May 1943, Allied sea and air forces won a stunning, dramatic, and vital victory over the largest and most powerful submarine force ever sent to sea, sinking forty-one German U-boats and damaging thirty-seven others. It was the forty-fifth month of World War II, and by the end of May the Germans were forced to acknowledge defeat and recall almost all of their remaining U-boats from the major traffic lanes of the North Atlantic. At U-Boat Headquarters in Berlin, despondent naval officers spoke of "Black May." It was a defeat from which the German U-boat fleet never recovered.

Black May is a triumph of scholarship and narrative, an important work of history, and a great sea story. Acclaimed historian Michael Gannon, author of Operation Drumbeat, has done enormous research and produced the most thoroughly documented study ever done of these battles. In his compelling historical saga, the people are as significant as the technical information.

Given the strategic importance of the events of May 1943, it is natural to ask, How did Black May happen and why? Who or what was responsible? Were new Allied tactics adopted or new weapons employed?

This book answers those questions and many others. Drawing on original documents in German, British, U.S., and Canadian archives, as well as interviews with surviving participants, Gannon describes the exciting sea and air battles, frequently taking the reader inside the U-boats themselves, aboard British warships, onto the decks of torpedoed merchant ships, and into the cockpits of British and U.S. aircraft.

Throughout, Gannon tells the Black May story from both the German and Allied perspectives, often using the actual words of captains and crews. Finally, he allows the reader to "listen in" on secretly recorded conversations of captured U-boat men in POW quarters during that same incredible month, giving intimate and moving access to the thoughts and emotions of seamen that is unparalleled in naval literature. Rarely, if ever, has the U-boat war been presented so accurately, so graphically, and so personally as in Black May.

Genres: History, World War II, Nonfiction, Military Fiction, War, Military History, Naval History

702 pages, Kindle Edition

First published January 1, 1998

About the author

(1928-April, 10, 2017)

Michael Gannon was a University of Florida history professor who was also a recognized expert on Florida history, particularly from its Spanish colonial founding through the Civil War. He spent most of his career in Florida.

Librarian’s note: There is more than one author in the Goodreads database with this name.

Reviews

[Michael Burnam-Fink · Rating 3 out of 5]

Black May is a serious, if somewhat scattered account of the crucial finale of the Battle of the Atlantic in May 1943. Gannon was a real historian, and this book draws heavily on primary sources like the logs of vessels involved and interviews with surviving captains, and uses the techniques of statistical analysis to show that even before May 1943, the U-boat was on the decline. The narrative and analytic aspects of the book never quite gel, leaving an unfair impression of amateurism.

The crucial moment was the battle of convoy ONS 5. In early May, 43 merchant ships returning from Britain to North America, and escorted by 16 Allied warships, faced off against several wolfpacks containing 43 U-boats over the course of a week. During the week-long battle in awful weather, 13 Allied ships and 6 U-boats were sunk. ONS 5 paid a high price by any standard, but it was the last time. Two later convoys in May were defended with no losses, and after, Donitz withdrew the U-boat arm from convoy action, making pinprick attacks at ships sailing independently in distant oceans. Britain's material security was ensured, and resources flowed from overseas to the fronts, leading eventually to the collapse of Nazi Germany. Though unheralded and fought over trackless ocean, the Battle of ONS 5 was as decisive as Trafalgar or Tsushima.

The role of technology is hard to overstate, and this book punctures several myths. The key technology on the Allied side was HF/DF, radio direction finding, which alerted convoys to the chattering wolfpacks. The U-boat staff considered it impossible that HF/DF equipment could be made small enough to mount on a destroyer or similar boat. Contrary to the popular image of Bletchley Park, during this period the Enigma was not broken, and even when it was the delays in decryption meant that the information was of little tactical importance. Conversely, the Nazis had broken the Anglo-American Naval Cipher No 3, and had inside knowledge of convoy routing. Neither side's cryptographic establishment seriously considered that their own codes were insecure.

Allied weapons in 1943 were also gaining a comprehensive superiority. The combination of 10cm radar and the Leigh light allowed for aerial night attacks, taking away a key refuge for U-boats recharging their batteries and moving into attack position on the surface. The hedgehog mine projector, though difficult to use, fired impact-fused charges that would destroy a U-boat with a direct hit. Depth charges, which exploded at a set depth, were surprisingly inefficient at killing the tough little U-boats. Though in a tactical sense, a U-boat forced away from a convoy was a victory, and a damaged boat that had to retreat and be repaired was an operational victory. More novel weapons like homing torpedoes and aerial rockets, cemented Allied technological superiority. The U-boat arm introduced their own tricks, including new types of torpedoes that would swerve though a convoy, and the potentially transformative Type XXI "electroboat" in 1945, but it was too little too late. It took a shocking 6 months to develop an effective radar warning receiver for the 10cm radar, and unlike American submarines in the pacific, U-boats were never equipped with their own radars and so fought at a disadvantage in the often foggy North Atlantic.

And simple weight of numbers bore out. Once the Liberty Ship program got started, U-boats simply couldn't sink merchantmen fast enough to destroy the Allied fleet. New escorts ship, corvettes, frigates, escort carriers, and destroyer escorts, were quick to build and while they lacked the speed to keep up with the battle fleet, they were more than capable of defeating U-boats. The inefficient Nazi industrial machine simply couldn't keep up, aside from the immense fortified U-boat pens along the Atlantic coast, which protected docked U-boats from bombing.

The last aspect of the battle is the human. Both sides fought magnificently. Allied merchant mariners suffered the highest proportional losses of any branch on the Allied side. The U-boat arm suffered the highest proportional losses, period (even being a Kamikaze pilot was more survivable), and yet they continued to sortie. However, the Allies developed effective defensive tactics based around teamwork and aided by the statistical techniques of operational research. Donitz fought his war by remote control, and this effort was a failure. Massive wolfpacks like the ones that savaged ONS 5 allowed other convoys to cross without contact. The constant radio traffic enabled Allied HF/DF and decryption efforts. And despite the concentration of force, U-boats never seemed to attack in large numbers. It took several escorts to fend off a single U-boat, so in theory a dozen or U-boats attacking simultaneously from all directions would overwhelm the escorts and sink much of the convoy. Yet despite Donitz's control, this simply didn't happen.

There are plenty of interesting nuggets in Black May, but I can't recommend this book to anyone but naval warfare buffs with several other Battle of the Atlantic books on their shelves.

[Stefanie Robinson · Rating 4 out of 5]

From April 29 to May 24, 1943, German U-Boats took heavy losses during the Battle of the Atlantic. Prior to this, Allies had been losing ships at a much heavier rate than their opponents. At the this period, there were about 240 U-Boats that were operational, and 118 of those were at sea. One of the most notable death's during this period was the son of Admiral Donitz, which I had no clue about before reading this.

I have had this book for a long time, and I wish that I would have gotten around to reading it sooner. This was a very informative book. I am much less knowledgeable about sea battles during World War II than I would like to admit, so this book was thoroughly beneficial to me. The research was done very well, and the writing was very interesting. I burned through this book, because it was dramatic. I am just a bit late getting to my reviews because I was gone all weekend. If you are looking to learn more about U-Boats or sea battles, I would strongly suggest picking this book up.

[Grace Emma · Rating 5 out of 5]

I love buying and reading these types of books.
Boats, yachts, historical events and books about the sea are generally excellent. If there are sequels in your series, I would love to read them.

The beauties of owning the books of important authors cannot be discussed. I'm looking forward to your new books.

For friends who want to read this book, I leave the importance of reading a book here. I wish good luck to the sellers and customers...

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[Rachel Parham · Rating 5 out of 5]

In this follow up to Operation Drumbeat, Michael Gannon takes us back to the Battle of the Atlantic, and specifically to the war fought between the German U-boats and the Allied convoys in the tumultuous waters of the North Atlantic. But where Operation Drumbeat focused more on the human element - telling the story of the merchant shipping slaughter on the American eastern seaboard in early 1942 through the adventures of one U-boat and her daredevil captain - Black May is far more technical... and technological.

That is not to say Black May isn't an incredible read, but only for those nerds, like myself, who are excited by details like the size, weight, explosive power, and speed of the Mark torpedoes, or how High Frequency Direction Finding technology (HF/DF or "Huff Duff") can pinpoint a submarine's location in the waters around you with lethal accuracy. When it comes to creating personal connections between you the reader and those long ago sailors fighting on the front lines of World War II's most decisive theater, which Gannon fostered so well in Operation Drumbeat, Black May is definitely lacking.

I still have to give the book 5 stars though because it is a thrilling ride through that eponymous month when the Battle of the Atlantic took a decisive turn in favor of the Allies. Although the tide had been shifting (pun intended) in the months leading up to May 1943, a confluence of factors came together over those 31 days to give the Allied powers the shove they needed to get ahead of the German Ubootwaffe. Gannon covers these factors in great detail, including the introduction and use of HF/DF and 10-centimeter radar on ships and airplanes, the improvements in torpedo technology, and the improvements in both air and surface ship attack tactics.

He dedicates several chapters to what he calls the Battle for ONS.5, an eastbound convoy that brought together these new factors and managed to fight off 40 U-boats over the course of several nights in early May 1943. In fact, the Battle for ONS.5 is the pivotal story in Gannon's book - it is through this convoy's anti-submarine warfare (ASW) strategies, and their ultimate success in scaring away one of the largest U-Boat "wolfpacks" assembled, that Gannon highlights exactly how much the above factors affected the overall submarine war.

So if you're a submarine nerd like me, Black May is a definite must for the TBR shelf. But if you want a more human story about submarine warfare in WWII, then check out Operation Drumbeat instead.

[Penecks · Rating 2 out of 5]

I don't like to do this, because I know there's someone out there who will love this book. But for most readers I just can't recommend it. Contrasting the work to "Operation Drumbeat", where most would have likely found the author, Black May tells a more overarching story of the turning point in the U-Boat war, mostly through reports of convoy battles, technological advances by both sides, and the air war against the subs.

Unlike Drumbeat, which to be fair basically writes itself as a high-seas drama, Black May gets into the nitty gritty. And I mean, it gets into it and bogs down terribly. The amount of useless detail in the text is quite astonishing. Nearly every sentence contains parentheses and quotes with random things that don't matter, or coordinates that maybe one reader with a German naval map is tracking, or headings that would take hours to plot for even one engagement with several ships. By the time one has crunched through a single statement, they have forgotten the information at the start of it, much less what is even happening in that paragraph. In a sick twist, the prologue and first chapters are especially guilty of this, possibly causing some to toss the book in a rage.

Where Gannon avoids this, the book actually reads quite well. The actions of high commanders, airmen, and innovation of new technologies are interesting. The translated "bugged conversations" of U-boatmen are a good addition, as is the epilogue about the fate of the U-boats. But trawling through the cargo list of a merchantman to get to the good part may strain the heads of even the hardiest of WWII readers.

[Steven Hull · Rating 4 out of 5]

Note: I read the paperback edition, not the Kindle edition.

The U-Boat menace was one of the few threats that kept allied leaders Winston Churchill and Franklin Roosevelt awake at night. Fighting the U-Boats while trying to keep Great Britain and other allies supplied with food, weapons, and other essentials was a losing proposition for the allies during the early years of the war. This book is the story of how the U-Boat threat was abruptly met in May 1943.

Gaining the upper hand in this war was difficult. Major allied technological advances and changes in tactics played key roles. As these advances were being created, the Germans made few improvements of their own. As a consequence, improved radars, more aggressive tactics based on statistical analyses, and the allied air coverage of entire convoy routes all coalesced in May 1943 to create unsustainable U-Boat losses. From this point on the U-Boats never again threatened to turn the course of the war in Germany’s favor.

[Robert Lloyd · Rating 3 out of 5]

Well researched but hard to read

First off, the author did a good job in meticulously detailing submarine warfare during world war two. It's because of this attention to detail and obvious hard work that I would feel guilty giving a lower rating. Having said that, I found this book impossible to read at times due to at the same time being overly detailed. I found that the author would spend an inordinate amount of time focusing on minutia at the expense of the overall narrative. Though I love history and feel it's important to understand details, I felt like I couldn't really relate to parts of the book unless I had some kind of engineering degree. There were times where the narrative became more readable and interesting, however it often took patience to make it there. This book would perhaps be more enjoyable to a more technologically minded reader, and would be more challenging to a casual reader of history.

[David Sears · Rating 4 out of 5]

Meticulously researched and documented account of how the Battle of the Atlantic finally turned in the Allies' favor. It is not an easy read because of all the detail Gannon provides. But it is an essential source. Gannon stops frequently to explain terminology, which often slows the pace to a crawl-and challenges the average reader's concentration. Gannon was an American academic with a decidedly British slant on the history of the Battle of the Atlantic. He can be very persuasive in his judgments though sometimes they are too pat--lacking a full appreciation of the confusing circumstances inherent in war. Operation Drumbeat, his earlier volume, along with Black May, offer a counterpoint to Clay Blair's two volume account: Hitler's U-boat War. Both authors tend to be encyclopedic in their approach to the material--often reaching opposing conclusions.

[Iain · Rating 3 out of 5]

A solid read but not as good as its predecessor, "Operation Drumbeat." Here Gannon's prose are often awkward, filled with commas and parenthesis. The narrative frequently lags and repeats itself. Conventions such as giving the name of each submarine's commander can not help but break the narrative flow. The entire chapter on clandestine crew interviews seems forced, as though included to fill the page count.

Which is unfortunate because this was great period in the Battle for the Atlantic. It was at this point in the war that the tide turned strongly against the German submariners and perhaps even Gannon's skill can't avoid the monotony of reporting on defeat after defeat.

[wayne · Rating 1 out of 5]

repetitious, clinical.... unimaginative writing just a technical description of actions... regurgitating historical records without much creative effort or real author input.
boat attacks at x angle. launches depth charges. hit miss... etc etc.
once you've read about one attack it repeats over and over.
not a good tribute to those who were involved in the activities, doesnt convey what they went through, and thought and felt.
Better to read a fictional account The Good Shepherd.

[Bob McNamara · Rating 4 out of 5]

Superior account of the U-Boat war in the Atlantic from 1942 into 1943 when the tide was turned. Wonderfully descriptive battle actions and highly technical info concerning anti-submarine weaponry. A must for anyone interested in the Atlantic War.

[D. L. · Rating 2 out of 5]

All the facts about WWII submarine warfare in the N Atlantic. Problem is that the author provided ALL the facts rather than weave a gripping story about this critical time and place in history.

[Hotrats · Rating 4 out of 5]

Very detailed.

[Garry · Rating 4 out of 5]

7/27/2021

[Paul Horstmann · Rating 3 out of 5]

An almost too meticulous treatment of the war in the Atlantic. Being somewhat familiar with submarine warfare, I did enjoy it.

[Cropredy · Rating 4 out of 5]

I was so impressed with Gannon's earlier book 'Operation Drumbeat" that I decided to immediately read the successor book "Black May". What a well-told story thhis is and from so many viewpoints. The primary story is that of convoy ONS 7, a 7 knot merchant ship convoy sailing from Britain to North America, guarded by a well-trained escort of destroyers and corvettes.

The Germans arrayed their largest force to date against this convoy and the battle raged on for days in all sorts of weather. Contrary to popular conception, breaking the Enigma code played no role at all as messages weren't decrypted until long after the battle.

The result was a stunning defeat for the U-Boat arm that led to a steady, if not precipitous decline in merchant ship sinkings throughout the rest of the war. As the author points out, this convoy battle could be thought of as the "Midway" of the U-Boat War.

So, why is the book so good?

1 - It is told from first person accounts in both the submarines, convoy escorts, and merchant marine survivors.
2 - It goes into great detail on the role of Operations Research in devising effective ASW tactics.
3 - It includes the simultaneous (month of May '43) air campaign against U-Boats transiting the Bay of Biscay
4 - There are secretly-recorded dialogues between German U-Boat POWs providing an insight into the minds of the crew
5 - Each attack and counter-attack is well-detailed, putting you in the U-Boat, destroyer, corvette, or airplane as it happens
6 - There is wrap up analysis that makes you understand how the Battle of the Atlantic was won and lost through a variety of 'systems' - technologies, tonnage, mathematics, leadership, and more.

[Hildo · Rating 2 out of 5]

Interesting; provides a broad view of the U-boat war in the month that the Allies got the upper hand. Focuses on a number of interesting characters and events while describing the broader story. Exhaustive notes and references.

The e-book is terrible. It gets a few things right - the footnotes are at the end of the chapters, not intermixed with the text; the endnotes are properly hyperlinked; and the chapter with text transcripts mostly gets the layout right. Apart from that, it's full of OCR errors and inconsistent formatting. The letter i and the number 1 are used interchangeably; ditto for the letter o and the number 0. Hyphens and m-dashes are interchanged. Italic and smallcaps are sprinkled throughout the text in inconsistent manner. "Hitler" is sometimes spelled "Hider". Admiral Donitz does without the umlaut on the o in about a third of the times his name is used. Paragraphs contain semi-random italic words. The publisher should be ashamed to release an e-book in this condition.

[Bas Kreuger · Rating 3 out of 5]

The first part of this book is riveting, the story of the ONS-5 convoy intermingled with the way the U-boat war had developed since 1941, the technical side of electronic warfare at sea, the intelligence side of codes and Enigma, the weapons side with depth charges, torpedoes etc, operational research by the 'boffins'.
Gannon weaves these elements in a gripping way that also gives good insight in where the tables were turned during that fatefull convoy journey.
In my view the book should have ended there. He goes on describing endless U-boat vs Allied air or escort battles that don't add much (if any) to the central story of Black May. Finally, he devotes pages and pages to conversations between captured U-boat men and those men and other German POW's. While interesting for the general trend of how the U-boat crew saw the war at sea through their own eyes, Gannon should have condensed this into an analysis plus a few examples.
So the first 50% of the book would get 5 stars, the second 50% brings it down to 3 stars.

[Au Yong Chee Tuck · Rating 5 out of 5]

This book is the non-fiction version of Nicholas Monsarrat's "The Cruel Sea." Readers who enjoyed reading about "HMS Compass Rose" in "The Cruel Sea" will find many more corvettes in "Black May."

There was no such thing as the phony war in the grim, relentless Battle of the Atlantic. This Battle started on the outbreak of hostilities and there would be no let up in the struggle against the U boats until the final surrender.

The Allies had the short end of the stick until May 1943. They had suffered such immense shipping losses that they even considered abandoning the convoy system.

Then came "Black May" in 1943 when Allied air and sea escorts sank 41 U boats and damaged another 37. It was a remarkable achievement considering that the average rate was then one U boat sunk per day.

How did the Allies reach this turning point? This is their story, well researched and superbly told by a Professor Emeritus of History.

[Thibaldo Manrique · Rating 5 out of 5]

A great history book of WW II

An excellent book that makes you feel you are right there with the fighting men both in the Uboats as well as in the planes and ships that attacked and destroyed them.

A very true to life account that brings the ungrateful realities of war to the reader. From tactics and strategies, both successful and not, to moral issues, to technological breakthroughs and the problems politics play on their deployment, a very entertaining look at the whole.

I particularly liked that it is very clinical, with no moral judgment, no wright or wrong. But rather what actually happened. It is a little dry because it strives, successfully, to be accurate and true to the original historical material.

It unfortunately has a lot of editing errors, which is very surprising, but does not take away from an excellent book.

It can be very much recommended as an excellent review of events towards the end of the war in the Atlantic.

[Jeff Rosendahl · Rating 3 out of 5]

I've had this book for nearly 20 years on my bookshelf and never read it. After finally getting through it, I'm wishing I could give it 3.5 stars. There's a lot of information here, although the text itself reads somewhat like a doctoral dissertation. Gannon says he's going to focus on several key convoy battles to illustrate how May 1943 was really bad for German U-boats, and he does that, but his background information was more interesting to read about in my opinion. Certainly a huge scholarly accomplishment and a lot of information about a WWII theater that gets short shrift in many works, and about a period in that theater that gets even less coverage. I especially like the discussions about how the English developed weapons and tactics designed to defeat the U-boats, whereas the Germans couldn't come up with new ways to maintain their tactical advantages.

[Ross Safford · Rating 4 out of 5]

One month out of the longest battle of WW2

One month out of the longest battle of WW2

This narrative covers more than one month of World War Two, but it does a good job of describing the action during May of 1943. For someone without appropriate knowledge, the frequent reference to longitude and latitude was a bit much. All in all, it was a good read, well worth purchasing.

[Antoine Vanner · Rating 4 out of 5]

Essential reading for anybody interested in WW2 at sea. This describes, in very considerable detail, the turning point of the Battle of the Atlantic. It is particularly effective in its communication of the relentless and exhausting - and indeed nightmare - nature of the fighting. This was one month in the longest campaign of WW2 and it reinforces the realisatio of just how much later generations owe to the men who made such sacrifies for Freedom enjoyed today.

[Betsy · Rating 4 out of 5]

A detailed look at a period which saw the beginning of the end for the U-Boat service in WWII. It is rather slow-going in spots but informative. There were brave men on both sides of the Atlantic War. Fortunately, it took more than bravery to win which the Allies proved.

[Mailmanr5 · Rating 3 out of 5]

This was a difficult read due to detail & stats however it provided a good argument for how the defeat of the U-2's in the Atlantic was a root cause for Germany's defeat & the UK survival.

[Glen · Rating 5 out of 5]

Love these Military History books.

[Vincenzo Rascionato · Rating 2 out of 5]

A couple of the chapters that talked about the overall war planning and challenges were very interesting and more than worth the read. However most of the book got into enormous detail on sub types, weapons, commanders, and battle details that got repetitive after a while.