Imperialism is a policy of expanding a nation’s authority by territorial acquisition or by establishing economic and political hegemony over other nations. Imperialism is one of the main causes for world war one. The reason why imperialism is the main cause is because many European countries wanted to have more power and the only way they could think about achieving more power was by expanding their territory. To expand their territory they needed more countries to make them part of their empire. Some of the countries that participated in this war were: Great Britain, France, Germany and The Netherlands. Because all these countries wanted to expand their territory, there weren’t enough countries to make them part of their empire, and I think