It was certainly not an 'existential threat', I mean 12 million Africans were taken as slaves between the 16th and 19th century,about 1.5 million died on board ship, Yet Africa do not name these nations as an existential threat.
You sure? Think about the kingdoms that existed in say what's now Tanzania, before the some guys from Oman showed up (and some guys from Portugal, and maybe a few earlier too)... they certainly seem to have vanished from the map.
