Seeing the tags you had indicated for your question, I have edited it to include the titles of the two literary pieces you tagged. The two works belong to different literary genres (novel/poetry) and two different historical periods. Adichie's novel was written in 2006, while Walcott's poem in 1962. Both are about Africa, although Half of a Yellow Sun is about the Biafran War of the 1960s while "A Far Cry from Africa" is about the Mau Mau uprising in Kenya in the 1950s. Yet, both works share important postcolonial features. They both argue against the inaction of the international community in the face of the massacres that they describe.
In addition, they represent the empowering of a quintessentially postcolonial subject/voice. At the end of Adichie's novel, we discover that the illiterate black servant Ugwu has educated himself and has been able to write a book on the Biafran War whose excerpts are interspersed throughout the narrative. Contrary to the expectations of readers who may anticipate the book to be the work of the white academic expatriate Richard, Adichie claims the rights of former colonial subjects to offer their own perspective on their own history. In Walcott's poem, the postcolonial character of the narrating voice is revealed by his torn attitude towards the conflict. As a Carribean writer who personally experienced colonial domination, Walcott shared the anti-imperialist agenda of the Mau Mau. but cannot bring himself to approve their violence and their aim to erase English cultural heritage from their country.