I would go for:
<span>North had a more widespread network of railroads available for delivering troops and supplies to the battlefield.</span>
Answer:
An act of war
Explanation:
The U.S. was not interested in war, however with the greatly increasing amount of America ships sunk in unrestricted submarine warfare, The U.S. was pushing towards war. The British intercepted the Zimmerman note that the Germans hoped the Mexicans received. This note was very threatening to the U.S. since it called for Mexico to invade America, including Texas and its borders. The U.S. most definitely didn't want a war on their own soil, against a neighbor.
I'm not an expert but I think it's Mesopotamia. If i'm wrong sorry! :)