How did British colonization influence the Nigerian Civil War?

Borders between nations in western Africa were drawn without reference to the original territorial claims.
British colonial leaders encouraged different groups to secede from the Nigerian nation.
The Nigerian Civil War led to Nigeria declaring independence from Britain in the 1960s.
The British colonial rule was over before the civil war, so it had no influence on it.

Question

How did British colonization influence the Nigerian Civil War?

Borders between nations in western Africa were drawn without reference to the original territorial claims.
British colonial leaders encouraged different groups to secede from the Nigerian nation.
The Nigerian Civil War led to Nigeria declaring independence from Britain in the 1960s.
The British colonial rule was over before the civil war, so it had no influence on it.