What event finally caused president Woodrow Wilson to ask for a declaration of war against Germany?

President Woodrow Wilson asked for a declaration of war against Germany after the sinking of the Lusitania in 1915 and the escalation of unrestricted submarine warfare by Germany. However, the final catalyst was the interception of the Zimmermann Telegram in early 1917, in which Germany proposed a military alliance with Mexico against the United States. This act, combined with ongoing attacks on American ships and a desire to protect U.S. interests, led Wilson to seek congressional approval for war on April 2, 1917.