Imperialism is the maintaining and extending of power over foreign nations, particularly through expansionism, employing both hard power (military and economic power) and soft power (diplomatic power and cultural imperialism). Imperialism focuses on establishing or maintaining hegemony and a more formal empire.
While related to the concept of colonialism, imperialism is a distinct concept that can apply to other forms of expansion and many forms of government.
Gunboat diplomacy is the pursuit of foreign policy objectives with the aid of conspicuous displays of naval power, implying or constituting a direct threat of warfare should terms not be agreeable to the superior force.
The term originated in the 19th century, during the age of imperialism, when Western powers, especially the United Kingdom, France, Germany and the United States would use their superior military capabilities, particularly their naval assets, to intimidate less powerful nations into granting concessions. The mere presence of warships off a country's coast was often enough to have a significant effect, making the actual use of force rarely necessary.