‘How’s the book?” my daughter asked when I was reading “Dark Invasion.”

“It’s okay,” I replied. “But it’s more like a crime novel than a history book.”

“So?” came her response. “You like crime novels.”

And therein lies my problem.

Professional historians are often suspicious of history books that seek blatantly to entertain. We’re a sober lot, which is a polite way of saying that we’re frequently dull. We have a remarkable talent for distilling the rich commotion of human experience into something boring and lifeless. The historian able to convey the drama of the past in a captivating yet accurate manner is unusual.

‘Dark Invasion: 1915: Germany's Secret War and the Hunt for the First Terrorist Cell in America’ by Howard Blum (Harper)

Given their oppressive solemnity, my colleagues will probably not like “Dark Invasion.” In style, it’s more like Lee Child than Richard Hofstadter. It breaks all the rules of historical writing, wantonly and repeatedly. Yet, partly for that reason, it’s wonderfully gripping. Howard Blum is a storyteller, not a historian. While I was reading this book, my professional standards collided with my personal taste. “Dark Invasion” became my dirty pleasure. It troubles me a bit that I liked it.

Blum’s subject is Germany’s efforts to sabotage American aid to the Allies in 1915, when the United States was still technically neutral. A collection of villains blew up supply ships, disrupted trade agreements and fomented discord in ordnance factories. They infected horses bound for Europe with lethal pathogens and attempted to assassinate the financier J.P. Morgan, who bankrolled aid to the Allies. Some of the saboteurs were ultra-patriots, others simple psychopaths. The man in charge of rounding them up was Capt. Thomas Tunney of the New York Police Department Bomb Squad. Like a typical crime-novel hero, he overcame bureaucratic inefficiency and meager resources to crack the case.

It’s all great fun, but as history “Dark Invasion” is seriously flawed. Inaccuracies abound. Before 1914, Britain had, Blum claims, “vowed to respond to any aggression against France.” No, that’s not true. The Stokes mortar makes an appearance in the narrative before it was actually invented. Throughout the book, Blum misunderstands the nature of trench warfare, with the result that he misinterprets the Allied need for U.S. artillery shells.

There’s something slightly cynical about this book. A rather insubstantial tale is beefed up by means of a large font, generous spacing, more than 40 blank pages and scores of photos. Gripping as this story might be, it’s not that important. Blum refrains from revealing how successful German sabotage efforts actually were. In fact, they had a small impact in comparison with, say, the German U-boat campaign. A more inquisitive historian might have asked why the Germans risked alienating American opinion with an espionage strategy of such limited potential.

Blum ratchets up the tension through creative license, in the style of a docudrama. This is understandable since his aim is to entertain. Historians are often hobbled in conveying drama because the archives seldom provide the evocative evidence of how people acted at precise moments. The historian who wants to write like a novelist therefore has to fabricate detail — the look on a face, the tone of voice, the slope of shoulders — from random indications of plausibility. What results is an account of what might have happened, not what did.

Blum insists that his reconstructions are based on exhaustive research. Yes, but that’s not the same as saying they’re true. In any case, historians usually subject evidence to rigorous tests of credibility. Blum seems unaware of a guiding principle of historical research: People sometimes lie, and spies lie almost all the time. Memoirs, in other words, are seldom accurate since they’re used to magnify an individual’s historical impact. Franz von Rintelen, the chief villain in “Dark Invasion,” was a sociopath whose business was deception. So why should we trust his recollections?

Narrative is the enemy of analysis. The writer intent on telling a good story often neglects the lessons to be learned. Such is the case with “Dark Invasion.” Almost as an afterthought, Blum argues that his book “is a story of the United States finding the will, the commitment, and the strength to become a world power.” That is his most profound insight and deserved more development. At the outbreak of war, Great Britain rounded up suspected enemy agents, executed most of them and was done with the problem. Not a single act of sabotage occurred in Britain during the war. In America, agents were allowed to carry out their mischief virtually unhindered. Granted, American neutrality made policing difficult, but that’s not the real reason for the susceptibility to sabotage. America suffered for her naiveté, her inexperience in the sordid side of international affairs. An espionage law was not passed until 1917. For Rintelen, spying was an expression of cultural contempt. America, he decided, “was too soft, too trusting, too unprepared.”

There are important lessons lurking here, but Blum misses most of them. Does it matter that the book is as insubstantial as a factory loaf of white bread? I read crime novels for entertainment, not enlightenment. They’re bubble gum for the mind, forgotten a week after finishing. That’s the case with “Dark Invasion.” I loved the cleverly crafted tension. It’s a bit of harmless fun that, with further embellishment, will make a wonderful movie. Every once in a while, it’s nice to stop being a historian. Professional standards are, however, difficult to jettison. In the midst of the drama, that nagging voice whispers, “But . . .”

Gerard DeGroot is a professor of modern history at the University of St Andrews and the author of the forthcoming “Back in Blighty: The British at Home in World War One.”


1915: Germany’s Secret War and
the Hunt for the First Terrorist Cell
in America

By Howard Blum

Harper. 474 pp. $27.99