Answer:
One reason is to simply expand their religion. Another would be to acquire more resources like exotic spices and such. Another being to dominate.
China fought for the ALLIES, specially in the Pacific Front against Japan, losing more than 15 million people.
The Soviet Union fought for the ALLIES on the Eastern Front, facing the German forces and losing more than 20,000,000 people.
Italy fought for the AXIS, helping Germany at the Mediterranean Front. It lost about 500,000 people.
Germany fought for the AXIS. Its attacks were held all across the world, from the Mediterranean to Eastern Russia, including North Africa and the Atlantic Ocean. It lost about 7 million people.
The United States fought for the ALLIES. US forces joined the war in 1941, after the attack on Pearl Harbor. Its casualties reached 420,000 deaths.
