If you asked someone what the worst naval defeat in American history was, I guarantee you that 99% of the time that person would respond "Pearl Harbor!" Unknown to many today, German U-boats operating off the Eastern coast of the United States, the Caribbean, and the Gulf of Mexico sank more than 600 merchant ships in a six month period beginning in January 1942. During the first three months of this campaign U-boats ranged along the shoreline with virtual impunity, hiding underwater in the daytime, slipping into the shipping lanes at nighttime. With the coastline brightly illuminated, merchant ships passed by like targets in a shooting gallery.

Operation Drumbeat, billed as "The Dramatic True Story of Germany’s First U-boat Attacks Along The American Coast In World War II," was published by HarperCollins as a hardcover in 1990 and as a trade paperback in 1991. It is 512 pages long, divided into 13 chapters, and has 16 pages of black and white photographs. Several appendixes are provided, along with a lengthy list of notes and citations, a glossary, and bibliography.

This book focuses primarily on the initial deployment of five Type IX U-boats in what Admiral Donitz called Operation Drumbeat, or if you prefer German, Operation Paukenschlag. These five submarines sank 25 merchants without reprisal from the United States Navy, and event which the author, Michael Gannon calls the "Atlantic Pearl Harbor." Gannon believes that the military impact of Drumbeat was far greater than the attack on Pearl Harbor. According to him, the primary effect of Pearl Harbor was to cripple obsolete battleships in shallow water, whereas Drumbeat came close to cutting off the supply of oil between the US and Great Britain.

U-123, commanded by Kapitänleutnant Reinhard Hardegen, serves as the focal point for Gannon’s narrative. In his two Drumbeat patrols, Hardegen sank 19 merchant ships, one of them barely 20 miles from New York City. Gannon recalls 123’s near-sinking at the hands of a Norwegian factory ship, it’s encounter with the Q-Ship Atik, and the infamous torpedoing and shelling of the tanker Gulf America just two miles from Jacksonville, Florida.

Operation Drumbeat also takes us inside the offices of the British Operational Intelligence Centre (OIC) and Bletchley Park, where the German Enigma ciphers were decoded. Gannon discusses how the OIC kept track of the five Drumbeat boats with extreme accuracy on a nearly hourly basis and passed the information along to the American Office of Naval Intelligence (ONI), who were regardless taken completely by surprise when they finally arrived.

The third major element of Operation Drumbeat centers around the United States Navy’s unpreparedness at the beginning of the war and the perceived dereliction of Admiral Ernest King, Commander-in-Chief of the US Fleet. Admiral King is the target of a number of sharp criticisms by Gannon, who makes Clay Blair’s comments in Silent Victory seem like child’s play in comparison. There were a couple of times where even I was stunned by Gannon’s blistering attacks.

The most surprising revelation, or perhaps the most shocking, is that we had accurate intelligence on U-boat positions and 25 of the most modern destroyers at our disposal, and didn’t do a thing to take action against Donitz’s first wave. The U-boat War was at a slump before Drumbeat; the British were routing their convoys around known U-boat positions, their escorts were gradually improving, Hitler had unwisely forced a major submarine redeployment to the Mediterranean, and merchant sinkings were at a six-month low. Why wasn’t the convoy system implemented sooner? Why wasn’t signal intelligence employed more capably? Why did Admiral King throw 27 months of hard-won British (and about eight months American) experience in fighting U-boats out the window?

Not easy questions to answer, and questions that Gannon, perhaps wisely, chooses to avoid answering. When one considers the almost total destruction of the U-boat fleet one year later, it’s hard to believe that a handful of them sank nearly a quarter of the Allied merchants lost during the war in only six months right on our doorstep. Gannon asserts the likeliness that King was an Anglophobe, which perhaps explains some of his decisions in the first few months of the war, but doesn’t explain why he never made any Anglophobic statements.

Thankfully, Operation Drumbeat is anything but a stodgy, top-heavy academic history book. You'd almost think that this was a Tom Clancy novel that takes place during World War II. If you've ever read The Hunt For Red October, you'll be experiencing Deja Vu. It has the same elements of that novel, forty years earlier: Submarines, espionage, last-second evasions, accurately reproduced radio transcripts, men in tiny offices moving flags around, and so on. The major difference being that I didn’t become hopelessly bored 200 pages in (sorry, Clancy fans, but I can’t bear the thought of having to read seven pages of a millisecond-by-millisecond account of a torpedo exploding.)

What sets Gannon apart from other historians is that he actually seems to understand how things work on a submarine. How many books have I read where everything is reduced to a trivial "boat goes up, boat goes down?" The reader gets a real sense of how complex a World War II-era submarine really was, and what it must have been like to live aboard one. It’s no Das Boot, but it still has a wonderful sense of verisimilitude.

The problems with Operation Drumbeat lie in Gannon’s occasional, and disconcerting, information overload, and with his gross underestimation of the emotional impact of Pearl Harbor. With 49 years of hindsight, yes, Gannon may be right in saying that Drumbeat was more damaging to the American war effort than Pearl Harbor. But in January 1942, the American people as a whole were not in the position to dispassionately analyze and bean count. At the time, it was a purely emotional situation.

The targets of Gannon's lengthy dissertations include almost a page comparing the German's Zeiss binoculars with their British counterparts, the phosphorescent qualities of the UZO crosshairs, and the inner workings of the G7e electric torpedo. All fine to know, but it brings the narrative to a crashing halt. A few of the sentences go on for nearly half a page, which gives the illusion that Gannon is ranting, instead of informing us, about the subject. Richard Rhodes may have gotten away with 200-word sentences in The Making of the Atomic Bomb, but Michael Gannon can’t.

Finally, many people have disagreed with the idea that Admiral King distrusted the British, though many more have agreed that he acted unwisely during Drumbeat. Even Edward Beach, one of the staunchest defenders of Admiral Husband Kimmel, considered King derelict in his duty. Of course, the final verdict will be the reader’s own. Being a civilian, I can’t throw down the final judgment upon King myself.

If you’re interested in the naval history of World War II, or more specifically the Battle of the Atlantic, you’re doing yourself a disservice by not reading this book at least once. It does have it’s flaws, and some will definitely feel that Gannon has an axe to grind, but it carries a strong message about the danger of failing to take heed accurate intelligence. It’s a lesson that’s true today, and a lesson that is still ignored.

Michael Gannon was born in 1928 and became a member of the American Field Service during World War II. Later, in 1968, he served as a war correspondent in Vietnam. At the time of this book’s writing he was a professor of history at the University of Florida. His most recent book was Florida: A Short History.