Answer:
My best answer would have to be the first one: soldiers had to fight in Asia and in Europe.
The US became involved in the war between fighting Japan, its allies, and the forces of the Nazi party in Europe. Since both Asia, Europe, North America, and many other countries joined this war formally and neutrally (in the form of trade and resource development) it was argued as a total war, meaning a war that encompasses the most largely involved number of nations to this day.
