On January 17, 1917, Arthur Zimmermann, the German Foreign Minister, sent an encrypted telegram to the German ambassador to Mexico: Because the British had pulled up every other trans-Atlantic cable at the beginning of the war, the telegram had to go through London, where the British had broken the German diplomatic code. The Brits leaked the text of the message to the Americans who published it in early March. It caused an uproar: What the hell were the Germans doing offering U.S. territory to Mexico? Zimmermann then committed what must be considered one of the top diplomatic blunders of all time: He admitted that the telegram was authentic. On April 6, 1917, the U.S. Congress declared war on Germany.