No writer is better placed than Chinua Achebe to tell the story of the Nigerian Biafran war from a cultural and political perspective. Yet, apart from an interview with Transition magazine in 1968 and a book of Biafran poems, Nigeria's most eminent novelist has kept a literary silence about the civil war in which he played a prominent role  until now. In his engrossing new memoir, There Was A Country, Achebe, now 81, finally speaks about his life during the conflict that nearly tore Nigeria apart in the late 60s.

In many ways, the early part of Achebe's life mirrors the story of early Nigeria. Nicknamed "Dictionary", Achebe was a gifted Igbo student and enthusiastic reader, a member of the "Lucky Generation" of young students who rubbed shoulders at top institutions under the tutelage of Oxbridge colonials. They were effortlessly absorbed into the media, industry and civil service, serving a Nigeria driven by optimism on its way to freedom from British rule.

By independence in 1960, Igbo people dominated commerce and the public sector in a land where the three biggest ethnic groups (the Yoruba, Hausa and Igbo) were jostling for supremacy. Achebe attributes Igbo domination to their self-confidence, inherent democratic values and adaptability, which were suited to Nigeria's modernising economy. But many Nigerians resented it, and Achebe admits that the Igbo could be cocky, brash and materialistic, though he rejects the popular suspicion that there was a pan-Igbo agenda to control Nigeria  his people have too strong an "individualistic ethic".

Six years after independence, corruption and electoral rigging preceded a military coup that overthrew Nigeria's first prime minister, the Muslim northerner, Abubakar Tafawa Balewa. Although most of the coup-plotters were Igbo, Achebe disputes that it was an "Igbo" coup, partly on the basis that its leader, Major Nzeogwu, had grown up in the north and was Igbo in name only. Nevertheless, the murder of Nigeria's northern leaders led to pogroms in which 30,000 Igbos living in the north were killed. The bloodshed culminated in General Emeka Ojukwu's declaration in 1967 that the Igbos' south-eastern region would secede from a country in which his people "felt unwanted".

Fearing the disintegration of Nigeria, the government blocked the secession with military force, backed by a UK government keen to protect its oil interests. Profoundly disappointed by this turn of events, Achebe left his job at the Nigerian Broadcasting Corporation in Lagos and returned with his family to the south-east, now calling itself the Republic of Biafra. The Nigerian army launched a three-pronged attack to subdue the Biafrans, who fought back assiduously despite being out-resourced. Achebe describes a wartime spirit that inspired Biafran engineers to build army tanks out of reinforced Range Rovers and to invent the infamous ogbunigwe (bucket bomb) with devastating effect. Though he abhors violence, Achebe cites these as evidence of the quality of the Nigerian people, and he laments the corruption that strangled such ingenuity.

In the middle chapters, memoir gives way to largely neutral historical analysis, with Achebe citing a range of voices, media reports and books. There are interesting insights into the war's two central players: Biafra's leader Ojukwu and Nigerian president, General Yakubu Gowon, both Sandhurst-trained young men. Rivalries between them and within their teams "confounded political science models". Possessing little administrative experience, the two men pursued ego-driven policies, and missed opportunities to end the conflict sooner. Achebe cites Biafran diplomat Raph Uwechue, who accused Ojukwu of choosing ideology over pragmatism when he rejected relief supplies from the British.

In the following chapters, Achebe's personal story re-emerges. Despite the war, he lived a remarkably productive life. Driven by his belief in the political obligations of the writer, he became Biafra's international envoy, promoting the cause in Canada, Europe and Senegal. He set up a publishing company with his close friend Chris Okigbo, and became Biafra's communications minister, writing a manifesto for the republic. He describes being part of an intellectual elite that came together to recreate a Biafran microcosm of Nigeria's early spirit, their ideals drawn from a mix of traditional Igbo philosophy, US-style liberalism and socialism.

As the federal army closed in, Achebe and his family moved from town to town before settling in his father's village. The atrocities proved inescapable: at a market, Achebe's wife Christie saw a bomb split a pregnant woman in two. Achebe relays such horrors  including the deaths of his mother and friend Okigbo  with stoic brevity; his strongest expressions of sorrow are his poems, such as the famous "Refugee Mother and Child". Reproduced from his 1971 Biafran poetry book Beware, Soul Brother, these verses are scattered between chapters, offering affecting interludes.

As the conflict dragged on, Biafra buckled under a blockade so brutal it provoked an international outcry: mass starvation, kwashiorkor and mental illness devastated the Igbo landscape, where vultures, those "avian prognosticators of death", circled overhead. Biafra was the world's first properly televised conflict, and millions across the world were appalled by the horrors flickering on their screens. Such people as Joan Baez, John Lennon, Martin Luther King and Karl Vonnegut galvanised international responses to the tragedy, in an age before "Africa fatigue" had set in.

By the time hostilities ended in 1970, three million Biafrans had died, in contrast to 100,000 casualties on the federal side. Igbos weren't mere casualties of war, Achebe insists, but victims of calculated genocide. Ojukwu, meanwhile, escaped to live in exile in Côte d'Ivoire, inviting accusations of cowardice. Achebe rationalises this move on the basis that if the Biafran leader had stayed in Nigeria, Gowon would have been less magnanimous and conciliatory towards Igbos after the war.

Igbos were reintegrated into Nigerian society, but still faced economic discrimination. Achebe offers an excerpt of an interview in which Gowon tries to justify the crippling £20 flat fee given to every Biafran wanting to convert their Biafran currency back to the Nigerian naira. This sense of persecution still persists today: Achebe believes that Igbo people are the engine of Nigeria's advancement, stifled by a corrupt elite that prefers power and mediocrity to meritocracy. Igbo ostracisation, he says, is "one of the main reasons for the country's continued backwardness". Some might call this supremacism, but Achebe is ultimately a Nigerian patriot who sympathises with ordinary Igbos, rather than any broad Igbo power structure.

The final chapter is an exhortation to better governance, in which he examines corruption, ethnic bigotry, state failure and the steps Nigeria must take to rehabilitate itself. This prescriptive wish list reminds us of the gap between theory and practice in Nigerian politics; it makes you pine for the likes of Achebe to govern. But sadly, he's not writing a manifesto; instead, we have in There Was A Country an elegy from a master storyteller who has witnessed the undulating fortunes of a nation, which  unlike young "Dictionary"  has yet to fulfil its potential.

 Noo Saro-Wiwa's Looking for Transwonderland: Travels in Nigeria is published by Granta.