Answer:
This document is known as the Zimmermann Telegram, sent by Germany to Mexico during World War I. The motives behind sending the document included diverting American attention and resources away from the European front by encouraging Mexico to declare war on the United States. Germany hoped that a conflict between the U.S. and Mexico would hinder the U.S. from supporting the Allies.
When the American public found out about the Zimmermann Telegram, it caused outrage and contributed to the U.S. decision to enter World War I on the side of the Allies. The revelation of Germany attempting to involve Mexico in hostilities against the U.S. fueled anti-German sentiment and swayed public opinion in favor of joining the war.