First of all, Chinua Achebe tries to negotiate the space between locals and colonizers in such a way as to seek a third space towards postcolonialism - going beyond internal and external problems of colonial society called Umuofia.
In Chinua Achebe's Things Fall Apart, he presents the African Igbo society as having culture and history like any Western society. This is to challenge the Western notion of African barbarism as described in Joseph Conrad's Heart of Darkness or Joyce Cary's Mister Johnson. For instance, in Conrad's Heart of Darkness, one of the north Nigeria towns and people are described like this
Fada is the ordinary native town of the Western Sudan. It has no beauty, convenience or health. It is a dwelling place at one stage from the rabbit warren or the badger burrow; and not so cleanly kept as the latter. It is a pioneer settlement five of six hundred years old, built on its rubbish heaps, without charm even antiquityâ€¦ Its people would not know the change if time jumped back fifty thousand years. They live like mice or rats in a palace floor; all the magnificence and variety of the arts, the ideas, the learning and the battles of civilization go over their hands and they do not even imagine them. 
Achebe claims that Western colonial rule has destroyed the traditional African society and its own indigenous culture. However, he does not blame the Western colonialism alone. He also criticizes the patriarchic male centered African society which oppresses the women and the social outcasts. It is clear that colonial domination is produced not only in the Western domination over the non-West but also within one country, such as the male over female, the ruling class over the ruled. When Okonkwo and some villagers were handcuffed and thrown in jail for several days, they were insulted and beaten from by the District Commissioner's men.
As soon as the District Commissioner left, the head of messenger,
who was also the prisoners' barber, took down his razor and
shaved off all the hair on the men's heads. They were still
handcuffed, and they just sat and moped.
'Who is the chief among you?' the court messenger asked in jest.
'We see that every pauper wears the anklet of title in Umuofia.
Does It cost as much as ten cowries?' [â€¦] At night the messengers
came in to taunt them and to knock their shaven heads together. 
The District Commissioner's men are Igbos from distant tribes, speaking a different dialect. They are description of a colonization bourgeoisie. They have an eye on accumulation of a fortune and high lank through turning against their clan. In this sense, While being conscious of the postcolonial theory, I read the colonization of the African Igbo society by the West and some insiders and the Igbo society's resistance to the Western colonial rule, as presented in Things Fall Apart.
The works of Achebe reveal opposition to inherent African culture earased by colonialism and inhumanity toward African. His works contributed to the developed of African prose by expressing the features of real Africans and the dignity of their cultural heritage in English. The Africans that he describes open the possibility of true African discourse that appeared in the age of post-colonialism. It was precisely the project of Things Fall Apart to tell the story of the colonized, to retrieve their history. In Things Fall Apart, he suggests that the Western colonial rule is something to be resisted by the African people themselves.
Here then is an adequate revolution for me to espouse-to
help my society regain belief in itself and put away the complexes
of the years of denigration and self-abasement. [â€¦] I would
be quite satisfied if my novels did no more than teach my readers
that their past-with all its imperfections-was not one long night
of savagery from which the first Europeans acting on
God's behalf delivered them. 
In addition, by writing in English, Achebe wanted this novel to respond to earlier colonial accounts of Africa; his choice of language was thus political. Unlike some later African authors who chose to revitalize native languages as a form of resistance to colonial culture, Achebe wanted to achieve cultural revitalization within and through English. Furthermore, he manages to capture the rhythm of the Igbo language and he integrates Igbo vocabulary into the narrative. By using a narrative method that expresses the African oral tradition in English, he shows us how English as the remains of colonialism can be used as a tool of post-colonialism. That is, an anti-colonial struggle must go along with another strategy for overcoming such internal problems within the African communities as dscrimination and other problems.
Moreover, Jean Rhys, a Creole from the West Indies living in Europe as an outsider, became acutely sensitive to the exploitation of women, especially Creole women. Rhys' protagonists, who have often been considered marginal or the other, are fully aware of their victimization and try not to lose their own identity by inscribing their voice and existence.
Antoinette in Jean Rhys' Wide Sargasso Sea is considered in comparison to Charlotte Brontë's Bertha. Displaced from her home in the West Indies through marriage to an Englishman, Antoinette, a Creole woman, was renamed Bertha by her husband. She was brought to England. Mad and confined in an attic, She becomes, figuratively speaking, a Creole prisoner in an English prison. She persistently asks herself about her identity. She refuses to accept the given identity as Bertha. In her dream she sets fire to the attic that symbolizes a prison of masculine and colonialist discourse. When she is jumping to flee from the attic, she recalls her home in the West Indies and the people there from whom she has consistently received spiritual encouragement ion her recollection.
To Rhys, Bertha, created by Brontë, is an impossible character who is represented from only the British colonial perspective. Therefore, Rhys brings Bertha out from behind the stage of Jane Eyre and gives her voice to tell her own story in Wide Sargasso Sea as Antoinette.
Rhys addressed her full attention to the spiritual crises that woman, especially Creole woman, meet with in her quest for identity against the odds of the dominant colonialists, patriarchal discourse. Her marginalized and silenced female protagonists end up in a seemingly miserable situation. However, the miserable reality experienced by them is not all that Wide Sargasso Sea is about. Her heroine articulates her anger at the distressing situation and her wish to find their true identity, by pursuing a liberating voyage toward her spiritual home.
Third, I plan to investigate how colonizers conquest in Things Fall
Apart and Wide Sargasso Sea.
In Things Fall Apart, Obierika bring Okonkwo the news of the white missionaries built churches and a few schools with them. Then, those converted a few local people to Christianity. In this way, West colonizers stood on the basis of colonization, emphasizing propagation of religion. Colonizers think it justifies their reason. Moreover, they induced natives to believe in the whites' religion, prescribing existing natives' religion is meaningless.
He told them that they worshipped false gods, gods of wood
and stone. [âˆ™âˆ™âˆ™] Evil men and all the heathen who in
their blindness bowed to wood and stone were thrown into
a fire that burned like palm-oil. But good men who worshipped
the true God lived forever in His happy kingdom. 
The white men treat the clans' natural-friendly worship as a false belief in God. It is imbued with a sense of purposes. Colonizers aim to spread their religion to the natives and make them have questions about their traditional rituals. Without any frequent contact with external civilization, the colonizers repeatedly say that their God is the best. It means, the white men stress a sense of western superiority.
"That I shall bring iron horses when we have settled down among them.
Some of them will even ride the iron horse themselves." 
It is a clever piece of camouflage tactics that the white men settle with the native community. They use humanitarian tactics to hide their wicked real character. The white men promise that they will take in 'iron horses' when they settle down among natives. This is also their trick. They use new modern conveniences to carry favour with the natives. Everything they do is studied.
But apart from the church, the white men had also brought a
government. They had built a court where the
District commissioner judged cases in ignorance. He had
court messengers who brought men to him for trial. Many
of these messengers came from Umuru on the bank of
the Great River, where the white men first came many
years before and government. Theses court messengers
were greatly hated in Umuofia because they were foreigners
and also arrogant and high-handed. 
The above quotation gives us useful information for understanding a true nature of imperialism. The white men build churches and bring a government in the town.
Now, move on to the Jean Rhys' Wide Sargasso Sea. Through the story, Rhys try to show the prosecution of and resistance against the contemporary patriarchal and imperialistic society and to establish women's status and identity through her self-recognition in those social situation.
Antoinette is a female subaltern who is doubly oppressed by males and colonialists. Two types of oppression coexist in Antoinette. First, there is patriarchal oppression by her husband, Rochester and her father, Mr. Mason. He married Antoinette for the money and that he tried to fool her into loving him, getting her hooked on sex to control her. He formulated Antoinette as a tool for accumulation of riches. According to the English law, women who married with English men have no right to accumulate own fortune. It means, English law subordinates woman's fortune to a husband. Using this law, Rochester seizes Antoinette's economic power. After screwing Antoinette out of her money, he shows desire to keep every circumstances on a tight rein. He aims to hurt her by taking her away from the island she loves.
I drew a house surrounded by trees. A large house. I divided
the third floor into rooms and in one room I drew a
standing woman- a child's scribble, a dot for a head, a larger
one for the body, a triangle or a skirt, slanting lines for arms
and feet. But it was an English house. English trees.
I wondered if I ever should see England again. 
Further, he refuses to learn and dismisses Antoinette's view. He wishes to be the arbiter rather than the recipient of knowledge, and he aims to assert his control over his wife by contesting her views. These are just like Western Europe's colonialization process.
The last suppression is the naming of Antoinette. Names are often core elements to build a sense of identity. Rochester calling Antoinette as Bertha, reinforces the split of her identity and the interruption of her mother, Annette. Antoinette's identity is always being defined in relation both to men and by men. At last she is set free only after setting Thornfield on fire and taking her own life.
In conclusion, Achebe, in Things Fall Apart, argues that the Western colonial rule should be put to an end by the African people themselves and that their resistance to the colonial rule should include overcoming the internal colonial problems in their own society. In Wide Sargasso Sea Rhys offers her the space in which she can tell her story about her relationship to Rochester, something that was hidden in Jane Eyre. Rhy's story embodies the mental, physical and economic exploitation of the female native. Her protagonists escape from the effects of Creole or black native stereotyping, such as being judged on mere suspicion by westerners, and come to represent themselves as independent subjects.