Imperialism's official definition is: "a policy of extending a country's power and influence through diplomacy or military force.
An example of this in history, is the rule of Great Britain in India. Great Britain established the British East India company that was established to create revenue for the English Empire. The English used their strong military power as a threat and the Indian natives knew they stood no chance if they were to fight them. The Indian people waited in patience until the 'peaceful warrior' Mahatma Gandhi emerged. Gandhi taught nonviolence as the way to resist, and he led many peaceful campaigns to show the British that they would not stand for injustice. Soon enough the British realized their wrongs and cut their losses and pulled all of their military from India.
Another example of imperialism was with the United States and Hawaii. Hawaii was ruled by Polynesian settlers until the United States got there. The United States realized the need for a military base closer the Eastern Hemisphere and this was their opportunity. They took control and turned Hawaii into a state. On August 21, 1959 was granted statehood and is a state until this day.
Another example of Imperialism was France in the Ivory Coast. The French took rule and kept it until 1960. After many battles, the French were forced to retract their troops from the now named Cote d'Ivoire.
The United States took control of Haiti in 1915 by order of Woodrow Wilson. The United States saw Haiti and knew that taking control over it would help with keeping control in Latin America. The United States used propaganda to convince the US citizens that they were not in the wrong but in 1942 the United States pulled all military troops and changed their focus onto World War II.