Okonkwos journey is one of self-imposed exile. So, too, is the journey of the Kurtz character in Conrads Heart of Darkness and Coppolas Apocalypse Now. Thus, Kurtz takes the place of the protagonist as being the symbolic character catalyst in Heart of Darkness and Things Fall Apart. The Kurtz character is more similar to the Okonkwo character than either Marlow or Willard. For this reason, Kurtz can be considered a default protagonist. The journey that Kurtz took has already happened, though. The reader of Heart of Darkness and the viewer of Apocalypse Now does not know how Kurtz got to that point. All we know is that Kurtz lost his mind, went insane, and is now a freak example of the heart of darkness of the human soul.
Even if their exile is self-imposed, Okonkwo and Kurtz remain a world apart from the rest of society. Psychologically and spiritually, Okonkwo and Kurtz are exiled. Their journeys are tragic in the sense that they are no longer in control of their bodies, minds, and souls. Regardless of how the Kurtz characters got to the center of the jungle and lost their minds, they are certainly portrayed as being insane. The journey is one that took them to a point at which no human being can return. They have seen the heart of darkness. Okonkwo is the same. He has not only seen but, like Kurtz, acted out the heart of darkness. The Kurtzes and Okonkwo have killed. They know what it is like to be insane and to be disconnected from the rest of humanity. Their journeys are not journeys to enlightenment but to hell.
Achebe actually portrays Okonkwos exile as also being at least in part self-imposed, even though he was technically banished from the community. After all, Okonkwo must take responsibility for the beating of his wife and the death of Ikemefuna.
His willful, selfish actions resulted in exile. The boys death directly predicated Okonkwos carelessness at the funeral. For Kurtz in both Heart of Darkness and in Apocalypse Now, exile is also self-imposed. The Kurtz characters became intimately familiar with the colonial enterprise of exploitation. Achebe explores the theme of colonialism too, and shows how colonialism is part of the heart of darkness. Colonialism is a theme shared in common with all three of these stories but is rendered in different ways.
The motif of the journey is common to Conrads Heart of Darkness, Coppolas Apocalypse Now, and Achebes Things Fall Apart. For Achebe, journey is a means of atonement and spiritual cleansing. Journey can be conceived of as a vision quest and a spiritual experience. Journey does not serve that same function for Conrad and Coppola. However, the protagonists of Apocalypse Now and Heart of Darkness both do undergo an unwitting vision quest. Their journeys into the heart of their respective jungle countries are characterized by visions of death and destruction. Like Okonkwo, Willard and Marlow learn of the horrors of colonialism.
Ironically, Okonkwo seeks to escape his father Unokas legacy but ultimately does not. His journey into exile does not actually heal him. Achebe suggests that all journeys lead back to the self; and that it is impossible to escape destiny. Also ironic is the encounter with Christianity is supposed to be into light but its not it is into greater darkness. It is also ironic that in Heart of Darkness and in Apocalypse Now, Marlow and Willard respectfully are neutral narrators whose journeys bring the central character into contact with the dark side of human nature. Things Fall Apart by Nigerian author Chinua Achebe accomplishes.