Needless to say, news of a German plot to incite Mexico to go to war with the United States further inflamed an already contentious debate, which manifested itself in perhaps familiar ways. Following the publication of Zimmermann’s memo, some anti-interventionists, who opposed American entry into the war, immediately decried it as a forgery. “There were accusations that it was fake news, that it was a hoax,” said Christopher Capozzola, a professor of history at MIT and the author of Uncle Sam Wants You: World War I and the Making of the Modern American Citizen. “There was definitely some sense that some people believed from the beginning that it was fake, but it was confirmed very quickly.”

Despite its incendiary nature and the breadth of the news coverage of it, history remains somewhat split about the material effect that the Zimmermann Telegram had on public sentiment or America’s decision to declare war on Germany just one month later. An entry in the National Archives concludes the communique “helped draw the United States into the war and thus changed the course of history.” Others argue that the impact of the telegram on pulling America into war was nothing compared to, say, Germany’s resumption of unrestricted submarine warfare, which threatened any ship crossing the Atlantic.

“All the newspapers I looked at [from the time] … had strong opinions about the telegram, but I couldn’t find a single newspaper that changed its opinion on intervention because of the telegram,” said Thomas Boghardt, who is the senior historian at the U.S. Army Center of Military History and the author of The Zimmermann Telegram. “It might have accelerated America’s entry into the war by a few weeks, but America was on its way into the war. You could make that argument, but let’s not mistake that for a cause.”

Despite the fallout, which involved German backpedaling and Mexican disavowals, the aftershocks from the incident may have been felt more in the arena of domestic politics than international politics. “Once Wilson learns about it, he doesn’t immediately release it,” Capozzola explained. “He eventually releases it as a weapon to intervene in a congressional debate” where the telegram is used to freeze out anti-interventionist lawmakers. “It was a pretty long slow slide into the war, but after the Zimmermann Telegram, it becomes very difficult for the U.S. to think that it can make any peaceful coexistence with Germany.”

As America moves closer to its World War I centennial this spring, there are different facets of l’affaire Zimmermann that echo in a 2017 context. It’s notable that the U.S. only caught wind of Zimmermann’s note because the British had been reading all the diplomatic correspondence that passed through the American Embassy in London, which at the time also included Germany’s cables to North America. Following the discovery and decoding of Zimmermann’s proposal for a German-Mexican alliance in January 1917, Captain William Hall, who headed up the British navy’s codebreaking outfit, held onto the telegram for weeks in part so he could construct a backstory that wouldn’t tip off the neutral Americans that their ally had been spying on them. Eventually, Hall, without consulting his government, would hand the memo over to Walter Page, the U.S. ambassador in London, a maneuver that very easily could have backfired.