Final answer:
Historically, Mexico desired a zone of protection in the territories of Texas, New Mexico, and Arizona, as promised by Germany in the Zimmermann Telegram during WWI. Defensive measures like border fences were also taken to protect against external threats.
Step-by-step explanation:
The zone of protection that Mexico wanted between themselves and their enemies refers historically to the territories of Texas, New Mexico, and Arizona. During World War I, the German Empire, via the Zimmermann Telegram, promised Mexico support in reconquering these territories in the event of a war with the United States. This was part of Germany's strategy to keep the U.S. military engaged on their own southern border and prevent them from joining the European conflict.
Meanwhile, Mexico had also established defensive measures along its own borders at various points in history to protect against insurgents or foreign freeloaders, as evidenced by references to the border fence built on the border with Guatemala. Additionally, tensions had been exacerbated by U.S. military interventions in Mexico, such as the pursuit of Pancho Villa by U.S. troops, which were seen by Mexico as invasions.