The leaking of a highly confidential telegram from Arthur Zimmermann, the German Foreign Secretary, to Heinrich von Eckardt, the German envoy in Mexico, on January 16, 1917, is one of the most written-about events in the history of international relations during World War I. Yet, Thomas Boghardt's excellent new study provides fresh details and interpretations while also opening up broader insights into the relationship among intelligence, diplomacy, and the rise of the secret state in the early twentieth century.

With Germany about to resume unrestricted submarine warfare, the telegram instructed Eckardt to offer an alliance to Mexico in the event of America entering the war on the side of the Allies. Mexico would have the prospect of “reconquer[ing] the lost territory in Texas, New Mexico, and Arizona,” and Japan—though at war with the Central Powers since 1914—would be invited to join the new coalition. Astonishingly, it was sent via the German embassy in Washington using U.S. diplomatic cables that had been made available by the American government after Germany's own transatlantic wires had been cut by the enemy. It was intercepted and decoded by British naval intelligence on January 17, and, having been passed to the U.S. State Department a month later, was printed in the American press on March 1, 1917. On April 6, the United States declared war on Germany.

Interpretations of this episode have tended to polarize around three conflicting claims. First, the telegram has been taken seriously as an indication of German war aims and an example of how “Kaiserism” threatened the freedoms of the Western world. Second, it has been cast as an act of stunning folly, not only because there was always a risk of it being intercepted, but also because the German Empire had no realistic means of helping Mexico retake its “lost territories,” much less of winning Japan over from the Allies. Third, it has been portrayed as a reasonable and even restrained attempt at self-defense that was then repackaged by the British and the interventionist East coast lobby to hoodwink the president and U.S. public opinion into entering a European war against America's true interests.

Boghardt's account shows that the story behind the telegram is considerably more complex than any of these theories suggest. Regarding German motives, he looks for the inner “rationale” that underlay the offer to Mexico, and he claims to find it in Zimmermann's previous involvement in attempts, since 1914, to stir up revolutionary unrest among subject peoples in Ireland, India, and the Middle East, as well as in his concern to improve his standing with Paul von Hindenburg and Erich von Ludendorff by minimizing the likely impact of U.S. intervention on Germany's ability to win the war militarily in Europe. Yet, in his understandable desire to avoid the “black-and-white” judgments of earlier writers such as Barbara Tuchman (The Guns of August, 1962), Boghardt doesn't quite make his mind up about Zimmermann. Was the telegram that bears his name simply a “half-baked, ad hoc diplomatic initiative” (143) that has to be read against the immediate circumstances of 1916-1917, or was it the product of more general policy “illusions” that had “pervaded the highest levels of the German government” (248) since 1914, if not before?

Boghardt nonetheless presents a vivid picture of Zimmermann's actions and motives after the telegram was published. He immediately verified his authorship, but chose to blame alleged security lapses in the German embassy in Washington, then headed by the liberal, pro-Western ambassador Johann Heinrich von Bernstorff, rather than concede that German diplomatic codes might have been broken by the enemy. The search for scapegoats then merged into the broader myth that Imperial Germany had been “stabbed in the back” by treacherous elements on its own side. Interestingly, both Zimmermann and Hans Arthur von Kemnitz, the key author of the telegram inside Wilhelmstrasse, later expressed admiration for the Nazis. This lends weight to Fritz Fischer's notion of a link between Germany's aims in World War I and the undermining and rejection of Weimar democracy on the part of the old elites after 1918.

The second dimension to Boghardt's book is the secretive world of cryptanalysis, or code breaking. Here he explores in impressive detail how Captain William Reginald Hall, director of the Royal Navy's Intelligence Division (NID) and a well-connected figure in transnational intelligence circles, was able to create a “personal fiefdom” (235) for himself inside Admiralty House and to deceive, in turn: the British Foreign Office (from which he kept the intercept for almost three weeks, and without whose permission he passed it to the Americans); his contacts in the U.S. embassy in London and the State Department (from whom he successfully concealed the true source of the intercept by generating a legend that the telegram had been accessed as it traveled along privately owned cables from Washington to Mexico City); and the wider American public (in the sense that the version of the telegram that appeared in U.S. newspapers on March 1, 1917, did not mention Britain's role and also made it look as if Germany was actively pushing Mexico into seizing U.S. territory rather than merely expressing passive support for such a venture). At the same time, Hall continued secretly to spy on American transatlantic cables and to feed the intelligence–obtained on a selective basis and at times of his own choosing–to his Whitehall superiors.

The third focus of the book is on Congressional, press, and wider public opinion in the U.S. Here Boghardt convincingly shows that the Zimmermann telegram did little to persuade isolationists of the case for war with Germany, although it did harden the resolve of interventionists, and, more particularly, helped to overcome the lingering doubts of Wilson. The president felt a sense of “personal insult” (140) upon learning that the German government had abused the State Department's offer to allow it to use its transatlantic diplomatic cables for what was assumed to be purposes of peaceful communication between Berlin and Washington. Wilson aside, it is clear from Boghardt's careful analysis that the U.S. went to war as a divided nation, with consequences stretching beyond 1918.

Overall, this is a stimulating read that makes a valuable new contribution to our understanding of how and why America entered the war. But the author's use of the “butterfly effect” to explain the ramifications of the Zimmermann telegram—whereby an apparently trivial incident in one part of the world can lead to huge, tornado-like upheavals somewhere else—does not quite do justice to the bureaucratizing effects of modern warfare, including the rise of the secret state. George Orwell's observation in his 1939 novel Coming up for Air, that the Great War had caused the emergence of “huge Ministries with hordes of clerks and typists all drawing two pounds a week and upwards for piling up mounds of paper,” is closer to the mark here. From this perspective, the interception, decoding, and publication of the Zimmermann telegram seem like a far less random, chance series of events. The odds were always in favor of discovery, manipulation, and carefully controlled disclosure.