Zimmermann’s audacious note aims to buy time by steering the US into a European war.

Unrestricted submarine warfare and the Allied blockade push Germany toward desperate choices.

Room Forty deciphers the note, copies another version, and hides the reveal while staying secret.

Wilson weighs neutrality against a catalyst: the publicized Zimmermann telegram and sunk ships.

Mexico, Japan, and Britain respond; the note reshapes policy, perception, and the war’s outcome.