For their part, the European merchants and trading companies called on their home governments to intervene and impose "free trade," by force if necessary.
It was these political, diplomatic, and commercial factors and contentions that led to the military conflicts and organized African resistance to European imperialism.
Direct military engagement was most commonly organized by the centralized state systems, such as chiefdoms, city-states, kingdoms, and empires, which often had standing or professional armies and could therefore tackle the European forces with massed troops.
This was the case with the resistance actions of the Ethiopians, the Zulu, the Mandinka leadership, and numerous other centralized states.
It developed in the nineteenth century following the collapse of the profitability of the slave trade, its abolition and suppression, as well as the expansion of the European capitalist Industrial Revolution.
The imperatives of capitalist industrialization—including the demand for assured sources of raw materials, the search for guaranteed markets and profitable investment outlets—spurred the European scramble and the partition and eventual conquest of Africa.
During the early phase of the rise of primary commodity commerce (erroneously referred to in the literature as "Legitimate Trade or Commerce"), Europeans got their supplies of trade goods like palm oil, cotton, palm kernel, rubber, and groundnut from African intermediaries, but as the scramble intensified, they wanted to bypass the African intermediaries and trade directly with sources of the trade goods.
Naturally Africans resisted and insisted on the maintenance of a system of commercial interaction with foreigners which expressed their sovereignties as autonomous political and economic entities and actors.
The differential interpretation of these treaties by the contending forces often led to conflict between both parties and eventually to military encounters.
For Europeans, these treaties meant that Africans had signed away their sovereignties to European powers; but for Africans, the treaties were merely diplomatic and commercial friendship treaties.
Between the 1870s and 1900, Africa faced European imperialist aggression, diplomatic pressures, military invasions, and eventual conquest and colonization.
At the same time, African societies put up various forms of resistance against the attempt to colonize their countries and impose foreign domination.
In general, small-scale societies, the decentralized societies (erroneously known as "stateless" societies), used guerrilla warfare because of their size and the absence of standing or professional armies.