Final answer:
The intercepted telegram urging Mexico to join Germany was called the Zimmerman Telegram. It offered an alliance with Mexico in exchange for Mexico causing disturbances along its U.S. border and promised to help Mexico regain the territory lost in the Mexican-American War.
Step-by-step explanation:
The intercepted telegram urging Mexico to join Germany was called the Zimmerman Telegram. It was sent by Germany's foreign minister and intercepted by British intelligence officers in January 1917. The telegram offered an alliance with Mexico in exchange for Mexico causing disturbances along its U.S. border and promised to help Mexico regain the territory lost in the Mexican-American War, including Texas, New Mexico, and Arizona.