00:00 The Zimmerman Telegram was a diplomatic message intercepted by British intelligence in 1917 that had the potential to change the course of World War I.

01:55 In the 1916 presidential election, the main issue was war and Woodrow Wilson's campaign slogan was "he kept us out of the war," but tensions with Germany and Mexico were building.

03:31 In January 1917, the German diplomatic service sent an encoded message to their embassy in Mexico through neutral countries and the United States, but the message was intercepted by the British Admiralty's Room 40, who had been decrypting most German coded messages throughout the war.

05:09 The Zimmerman Telegram revealed Germany's plan to initiate unrestricted submarine warfare and propose an alliance with Mexico to attack the United States, potentially leading to American involvement in the war.

06:57 The British had to come up with a story to explain how they obtained the decrypted Zimmerman Telegram without revealing that they had cracked the German code or intercepted American diplomatic communications, so they claimed to have bribed someone in the Mexican office to get a copy of the telegram and stolen the decrypted message from the Germans in Mexico.

08:33 The Americans were shown the decrypted Zimmerman Telegram and its code, leading to its public release, an uproar in the country, and the United States declaring war against Germany, which helped turn the tide in World War I.

10:05 The Germans had no benefit in having Mexico invade the United States, as Mexico would have gained mostly desert territory filled with armed English-speaking settlers, so instead the Mexican President used the telegram to negotiate recognition of his regime in exchange for Mexican neutrality in World War I, while the British kept the truth about the telegram hidden for over 25 years and the Germans suffered the negative consequences of the United States joining the war.