The Zimmerman Telegram was a secret telegram sent in 1917 by the German Foreign Office to Mexico. It proposed a secret alliance between Germany and Mexico. The Germans wanted this secret alliance in case the US entered WW1 on the Allied side, as they would have an ally in North America from where they could launch a direct attack on the US heartland. In exchange for military action against the US, Mexico would receive Texas, Arizona and New Mexico. This telegram, however, was intercepted by the British secret service and decoded. It's contents enraged the American public, and helped persuade the Americans to join the war on the Allied side. Slight ironic, considering the Zimmerman Telegram was trying to plan for this exact eventuality.
