In looking at culture clash in Achebe's Things Fall Apart, we will focus mainly on the late portions of the novel (from Chapter Fifteen to the novel's end). In this section of the narrative, missionaries arrive and undertake a mission of Christian salvation and colonization. English governmental bodies are also brought to bear in the region.
First, the whites appear as a rumor, talked about in a "woeful story." Described as "riding an iron horse," the first white man encountered is feared because he appears so different. Village elders in Abame consulted their Oracle, which told them "the strange man would break their clan and spread destruction among them." The men of Abame then killed the white man due to the Oracle's prediction. Not long after that killing, white men arrive in Abame with guns and effectively wipe out the village.
As evidence of culture clash, this episode presents a stark initial conflict between two peoples with little understanding of one another (and little interest in developing any understanding).
Pointing out more details of culture clash, we can look at how Okonkwo's son, Nwoye, is severed from his family by the missionaries and their religion.
"It was not the mad logic of the Trinity that captivated him. He did not understand it. It was the poetry of the new religion, something felt in the marrow."
Nwoye joins the Christians, adopting their religion and separating himself from his family.
This turn of events can be seen as an indirect product of the conflict expressly created by the missionaries that sought to turn the Ibo away from their traditional religion and to forget their gods. The missionaries preach that there is no compromise possible and that their views are the only valid views. To join them is to cast off one's history if one is of the Ibo people and culture. At least, this is how the missionaries are introduced and/or how they introduce themselves upon arriving in Mbanta-- seeking to save the local people by turning them away from a native religion.
Nwoye's decision to leave his home is also helped by Okonkwo's anger, which is both part of his character generally and part of a specific and focused response to the colonist mission in Mbanta.
The missionaries build a house in a forbidden region, demonstrating a lack of understanding of local taboos. They also receive outcasts (osu) as members of the church community. As the Christians and their converts continue to demonstrate a lack of concern for the Ibo customs and taboos, they are ostracized from the clan, a move that briefly creates an overt clash between the two cultures, putting them at odds with one another.
Later, when Mr. Smith takes the place of Mr. Brown, a woman is hanged for allowing her husband to mutilate their dead child according to customs that allowed the bodies of dead children to be treated in this way "to discourage it from returning." Smith's response is to say that "Those who believed such stories were unworthy of the Lord's table" and to have the woman "suspended" from the church.
As the missionaries and the foreign governments that accompanied them become entrenched, the tribes begin to lose cohesion.
"The white man is very clever. He came quietly and peaceably with his religion. We were amused at his foolishness and allowed him to stay. Now he has won our brothers, and our clan no longer act like one. He has put a knife on the things that held us together and we have fallen apart."
This speech from Obierka communicates one of the most important effects of the colonization program instituted against local customs and in opposition to traditional laws and cultural beliefs. While the missionaries who arrive in Umuofia and Mbante may be well-intentioned according to their own consciences, they are nonetheless pursuing a program of antagonism whose aim is to undo native traditions and cultures.
Obierka explains that a man, Aneto, is hanged because he acts on traditional customs that have been overturned by a white court that has received payment and support from a local family. The suggestion of self-interest and corruption implied here serves to negatively characterize the mission of the colonist occupiers in the region. Also, this episode demonstrates a basic conflict that exists when two codes of law are being enforced in the same area/village.
The clash of cultures can be seen as a conflict of interests in the novel as the fundamental interests of the colonizing peoples is to undermine the integrity of local traditions and cultures so that they can be replaced by European and/or Christian institutions of government and of faith.
For more information on Achebe and his life, check out this interview: