How does Chinua Achebe use settings in Things Fall Apart?

The main setting of Things Fall Apart is a series of Igbo villages in what is now Nigeria, just before, and at the start of, British efforts to colonize and Christianize the tribes. The setting is crucial because of that historical context and because of the way the tribal values have shaped the protagonist Okonkwo. There is a key change of setting in the novel, as well, when Okonkwo is exiled to his motherland for seven years. When Okonkwo goes to his mother's village of Mbanta, he is humbled; he is no longer a tribal leader. And yet, when all he can think about and look forward to is how he will regain his status and wealth when he returns to Umuofia.
The setting of Umuofia influences Okonkwo's character, though he deviates from his cultural norms in significant ways. The tribe values ancestors and traditions. Okonkwo respects these values only to an extent. He beats one of his wives during the Peace Week, which is strictly forbidden, and he disavows his own father for being poor and not masculine enough by Okonkwo's standards (he is a musician, while Okonkwo demonstrates his manly strength through wrestling and successfully farming yams).
When Okonkwo returns from exile, he finds that the tribe has fallen under the influence of the Christians. There are some rebels, but there are also some villagers who have converted. Umuofia is a changed place, and Okonkwo's priorities are no longer shared by many of his peers or by those of younger generations. The setting shows us the flaws in Okonkwo's character and how his inability to accept change leads to his downfall. However, the setting also allows Achebe to critique the methods and attitudes of the westerners who come to Umuofia and attempt to "pacify" (209) the African tribes.