The Twenty Years War

"Aro natives making road for us by order outside Bendi [Bende] Cutting bush with matchets" during the 'Aro Punitive Expedition', or Anglo-Aro war, 1901. British Museum.

Far from willingly conceding their territory to the military patrols, the people of Southeastern Nigeria opposed the British advance in more than three hundred pitched battles over a twenty year period, suffering at least ten thousand casualties. [...] Although violent resistance could not halt the British advance, it was effective in moderating and speed and thoroughness of that advance and in enabling Southeastern Nigerians to retain a measure of self-determination over the rate at which they absorbed technological and other changes.

– Robert D. Jackson (1975). "The Twenty Years War, Invasion and Resistance in Southeastern Nigeria 1900-1919".