That would be thoroughly appreciated
Ok
So similar to a lot of African countries, the territory that became Nigeria was formed by the British carving a random piece of land out of West Africa (along with Ghana, Sierra Leone). This colony contained over 200 distinct ethnic groups, but the 3 biggest were (and are today): Hausa-Fulani, Yoruba, Ibo.
Hausa-Fulani: Predominant ethnic group in the north. Pastoral/nomadic culture, with a few big trading cities linked to the Sahara trade (Kano, Sokoto, Daura). 100% Muslim. Historical government model: ruled by priest-warrior figures called Emirs. Very suitable for indirect rule (more on this in a bit). Largest population.
Yoruba: Predominant ethnic group in the west. Agricultural culture. At the time of conquest, dominated by traditional religions, although after the British took over, vast converted to Christianity/Islam (let's say 60/40 split). Historical government model: society was split into various tribes ruled by various kings, that warred with each other. A lot of people (captives of war) were sold into the Atlantic slave trade before Britain put an end to the practice in the 1800s. Very suitable for indirect rule.
Igbo: Predominant ethnic group in the East. Agricultural/trading culture. At the time of conquest, dominated by traditional religions/rites. Once the British took over, vast majority converted to Christianity. Historical government model was very democratic (every man in the village/town had a voice), as opposed to their big neighbors to the West and North. Following conquest, this region became very overpopulated, leading a lot of Igbos to migrate beyond their borders in seek of work/trading opportunities (also more on this in a bit).
Indirect rule: Because the British were better at colonizing than the French, they preferred to govern using indirect rule. They would find a traditional figurehead and let him keep his throne, and govern through this figurehead. Because the Hausas and Yorubas were used to this kind of rule, the British found it easy to govern Northern/Western Nigeria. Because the Igbos didn't have any sort of figureheads in their society, artificial ones installed by the British proved very unpopular. The resulting strife didn't make the Igbos look good from the British perspective.
Fast-forward to a few years before independence (1950s), post WW2...
At this point, Igbo people are all over Nigeria as traders and businessmen. They have a sizeable contingent in the Hausa dominated North. The British created parliament favors the Hausa/Yoruba over the Igbo. At independence, the first prime minister of Nigeria is from the North.
Fast forward to 1964-1965.
Igbo migrants are massacred in the North, in a set of violent pogroms. The ones not murdered run back to the East with only the clothes on their back.
Fast forward to January 1966.
A coup d'etat is initiated by Igbo junior officers. The prime minister (from the North), and senior military officers from the North and West are assassinated surgically, overnight. An Igbo officer not involved with the coup assumes power, but the instigators of the coup are not punished. To add insult to injury, the replacements for the murdered military officers are predominantly Igbo.
July 1966: a counter coup is executed by Hausa officers. The Igbo military head of state, as well as senior Igbo officers, are taken out overnight. In addition, after the coup success, more pogroms aimed at Northern Igbos occur. A non-Hausa officer from the North assumes power, but he does not punish the Hausa officers, neither does he do enough to protect Igbo migrants from the massacres ongoing.
1967: Fed up at the situation, a senior Igbo officer, Col. Ojukwu, threatens secession of the Eastern region, which was predominantly Igbo, but also contained a sizeable bunch of other minority tribes. His threats, supported by a seething Igbo nation, were for the most part dismissed by the military regime. After a few failed negotiations, the Republic of Biafra declares independence, raises an army, seizes federal facilities in the Eastern region, and seals all land/river entries to the region from the rest of the country.
1967-1970: the Civil War was one of attrition. Biafra fought mostly a defensive war, with the aim of forcing Nigeria to accept it's secession. Nigeria was in no mood to let Biafra go (it was a vital source of petroleum). So here is what the military regime did.
1. It blockaded Biafra from the Atlantic Ocean, preventing all but humanitarian aid from getting through.
2. Prior to secession, the Eastern Region was 1 state. The regime created 3 new states out of the region, making sure that 2 of the 3 states had majority-non Igbo populations. They effectively gave these states a good reason to support Nigeria against Biafra which was Igbo dominated
3. It began a bombing campaign against infrastructure deemed critical to Biafra (airports, bases, industrial clusters)
4. It initiated a 3 pronged invasion from the North, West and the sea (to the south), aimed at Biafra's center, with the aim of quelling the rebellion.
Biafra fought well against increasingly overwhelming odds, as supplies and food and morale started to dwindle. A lot of people died from bombs and disease and starvation. There were a few massacres (mostly aimed at Igbo civilians/unarmed combatants by Nigerian soldiers). Biafra attempted an invasion of the West in order to divert attention away from it's homeland and force international intervention but it failed. It took 3 years but in 1970, Ojukwu fled abroad and his second in command surrendered.
The Nigerian head of state is famous for insisting "no victor no vanquished" and his outward agenda was to pretty much, re-integrate Biafra into Nigeria and move on. This was accomplished with the aid of the oil boom in the 1970s which flooded Nigeria with petro-dollars. But the war has kind of been swept under the rug. I don't believe the country has done a full reckoning of the aftermath of the war, how it has impacted relations between Igbos and the rest of the country till today (there has been no Igbo president/head of state, ever), and how the region was deliberately neglected for years to the detriment of the North and West.
There you go. The literature is harrowing yet fascinating. Chimamanda Adichie's Half of a Yellow Sun is set in Biafra during the war... I'm more of a non-fiction/military geek though so that's where I've done a lot of reading.