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I know there were some cases of sub-Saharan African empires expanding out of sub-Saharan Africa. The Kingdom of Aksum/Axum had a foothold in Yemen, and Egypt fell under Nubian rule for a time. There might also be some other examples I'm unaware of.
So I can't help but wonder what other sub-Saharan African empires might've been able to hold territory outside of sub-Saharan Africa.