In both German and Italian unification there was on leading state.
The Japanese attacked Pearl Harbor for the main reason of tension in the Pacific. The Americans weren't necessarily in the conflict at this point, but were sitting in the Pacific watching the Japanese, if the Japanese were to grow in power, they can't have the Americans on their tail. The attack counterattacked the Japanese if you really look at it. Most people would relate the Pearl Harbor attacks as "poking the sleeping bear with a stick", and that's true. We turned the fighting back to the Japanese in the months after the attack. And four long years later, we dropped the "Little Boy" atomic bomb on island town of Hiroshima -- And the second bomb called "Fat Man" on Nagasaki 3 days later. The Japanese surrendered less than a month after the bombings. So, the attacks of Pearl Harbor really hurt the Japanese more than it hurt the Americans.
Answer:
I would consider the adoption of gun powder
Explanation:
gun powder changed the world and is still widely used today for guns, explosives and rockets.
It was because different states had their own dollars, and some places did not accept dollars from every state
