What are the factors that that led to European imperialism?

One factor that led to European imperialism was population growth after the end of the cycles of plague. The population increased, and European governments needed to search elsewhere for raw materials in order to feed their growing industrial centers. There was another spike in imperialism after the end of the Napoleonic Wars as Britain and France sought to colonize Asia and Africa. European nations looked abroad for new sources of timber, minerals, and foodstuffs. In order to curb dissent at home, many European nations looked to colonize far-flung areas; in some cases, the colonists sent to settle were not given a choice, as was the case of the British in Africa. By allowing religious and political dissenters to leave, European monarchs rid themselves of potential troublemakers as well as gained the work of these colonists as they shipped valuable materials back to the mother country.
Another factor was nationalism. In the nineteenth century, Europeans believed that they were destined to rule over the developing world. Rudyard Kipling's poem "The White Man's Burden" states that it is the job of the Protestant Briton to spread civilization and Christianity in these areas whether or not it was desired by those who lived there. In time, colonies became a source of national pride, and nations developed rivalries over who could own the most valuable pieces of land. An American, Alfred Thayer Mahan wrote a treatise on naval power which influenced European desirefor islands to serve as coaling stations. This led to further European colonialism, and eventually nearly all of the developing world would either be a European or an American colony.