British Foreign Affairs Office, London, February, 23rd 1917. In the afternoon, Arthur Balfour, the foreign secretary of the United Kingdom, hands the American Ambassador Walter Page a sheet of paper.

Accidentally sharing attack plans with a journalist in a group chat is bad. Causing a rising superpower to declare war on you ...

But as the war unfolded in Europe, an intercepted telegram sent by the German Foreign Secretary, Arthur Zimmermann, to the Mexican government inflamed the U.S. public opinion and was one of the ...