NEWPORT, R.I. >> In a secret telegram a century ago, Germany tried to get Mexico to join its side during World War I by offering it territory in the United States. Britain intercepted, deciphered and shared the “Zimmermann Telegram.”

Historians, seeing parallels to today, say there’s a lot to be learned.

They gathered at the U.S. Naval War College in Newport, Rhode Island, last week and discussed how a foreign government hacked a secret communication and used the information to sway American public opinion and policy. When it was released, there was a heated debate over whether it was real or what we now call “fake news.”

The message’s publication — and Germany’s resumption of unrestricted submarine warfare — was the culmination of a series of events that drew the United States into the war.

Fast-forward a century. Today, the U.S. intelligence community says Russia hacked Democratic groups during the presidential campaign to help Republican Donald Trump defeat Democrat Hillary Clinton. President-elect Trump says the DNC was “totally open to be hacked” and praises his future chief of staff for ordering “hacking defense” at the Republican National Committee.

“The greatest strategic threat the U.S. faces is the general ignorance of the past and how the past is with us every day,” said David Kohnen, interim executive director at the U.S. Naval War College Museum.

German foreign minister Arthur Zimmermann sent the telegram in January 1917 to the German representative in Mexico. Germany would resume sinking vessels without warning and Mexico could ally itself to reconquer Texas, New Mexico and Arizona, he wrote.

Germany wanted to keep the United States busy fighting Mexico so it couldn’t send troops and supplies overseas.

The British waited to share the information to avoid compromising their intelligence-gathering methods. But once the “German plot” appeared in headlines, President Woodrow Wilson had few options, said Kohnen, the conference organizer. The United States declared war April 6, 1917.

Retired Rear Adm. Samuel Cox, current director of the Naval History and Heritage Command, said he sees parallels with Russia’s recent actions, but stressed that England wasn’t trying to diminish U.S. influence in the world by discrediting its values and democracy.

Cox focused on how many people refused to accept the telegram’s authenticity because it didn’t fit with their preconceived notion of reality, which he said is a reminder of the importance of driving misinformation and rumor out of political debate.

“If you have an environment where the truth becomes optional, like we’re kind of facing today, once you’re in that environment it becomes difficult to break out of it,” he said. “People refuse to believe the truth because they can’t tell the difference.”

Other historians pondered the consequences of the Germans’ overconfidence in their abilities to encode messages. Cryptographers get too arrogant— they think no one will get into “my system,” said David Hatch, a National Security Agency historian.

“It was true in 1917 and it’s certainly true today,” he said at the conference.

Cox has sent a memo to naval leaders about the significance of the Zimmermann Telegram so the lessons learned could prove useful.