The Zimmermann telegram

In January 1917, codebreakers in Britain's secret Room 40 office intercept a telegram sent by German Foreign Secretary Arthur Zimmermann to Germany's ambassador in Mexico. The message lays out a proposed wartime alliance. If the United States enters the war against Germany, Mexico is to side with Germany and Japan, and Germany will help it win back Texas, New Mexico and Arizona.

This is narrative history and a work of non-fiction. Barbara Tuchman follows the British effort to decipher the message, then the delicate problem that follows: how to pass it to Washington without letting Germany learn that its codes have been broken.

She places the telegram within the events around it. The German high command has decided to resume unrestricted submarine warfare, Woodrow Wilson is holding to a strained neutrality, and relations between the United States and Mexico are unstable during the Mexican Revolution.

The account runs from interception to publication. When the telegram's contents reach the American press in early 1917, public opinion shifts decisively, and within weeks Congress moves toward declaring war on Germany. The book is useful for readers interested in the First World War, in intelligence work, and in how a single secret message helped bring the United States into the conflict.