Imperialism is when a country uses diplomacy or military force to extend a countries power
Examples of Imperialism
When the U.S. went to Hawaii they were using imperialism to take Hawaii by using diplomacy to make them want to join us
When Great Britain came to the America's they used military force to make the people there who were the Indians to leave or join Britain.
The U.S. used imperialism to make Puerto Rico join the U.S. They used military force to defend them from Spain and forced them to join us.
When the Spanish war reached the Philippines the U.S. defended them but when they did they claimed the Philippines as a territory.