It was Giuseppe Garibaldi, who unified Italy in 1871.
Scarcity of resources. The European countries and Japan didn't have all the resources they needed in order to keep up industrialization and a few other reasons. They resorted to taking over other lands in order the "cheaply" obtain the resources.
First of all... what period? because if you are talking about this time, I think it is becaise they want to feel powerful to be able to have more allied countries in any situation, they also do it because they want to control most of the world natural sources that other countries have.
The main reason why the twenties are sometimes called an "age of prosperity", especially in the United States, is that "<span>A.Incomes throughout the United States grew and the middle class held most of the wealth," due mostly to speculation in the stock market. </span>
