In January 1917, Germany sent the so-called Zimmermann Telegram, which implied that a Mexican alliance with Germany against the US would result in Mexico regaining territory taken from it by the US in prior wars and that Germany's forthcoming unrestricted submarine warfare campaign would guarantee defeat of the British and French. The British interception of Zimmermann's telegram and the German unrestricted submarine warfare against US merchant ships, soon afterward, were effectively both final justifications that President Wilson needed to request a declaration of war against Germany, in April 1917.