[1] During the Nigerian civil war (1967–70), Ahidjo provided valuable support to Nigeria's federal military government, led by General Yakubu Gowon.

[4][5] In November 1967, after initially declaring himself neutral in the conflict, Cameroon closed its border with Nigeria and banned shipments to Biafra of arms, medicines, foodstuffs, or other supplies.

[6] Still more surprisingly, Ahidjo publicly lambasted the nations who supported the Biafran secessionists – a group which included not only African states like Gabon, Ivory Coast, and Tanzania, but also France, one of Cameroon's most important patrons.

[7] This inaugurated "perhaps the finest hour" in 20th century Cameroon–Nigeria relations: during a state visit to Nigeria in September 1970, Ahidjo received Gowon's public praise for his support, and in 1972 the University of Lagos awarded him an honorary degree.

[3] On 11 February 1961, months after Nigerian independence, a plebiscite was held, under the supervision of the United Nations (UN), to establish the future of the areas along the Nigeria–Cameroon border which previously had been under British mandate.

[10] Ahidjo had campaigned for the total reunification of Cameroon, and he unsuccessfully protested the result of the northern vote at the International Court of Justice, alleging British and Nigerian interference, from "intimidation, open persecution and obstruction of all kinds, to shameless rigging".

As Cameroonian politician A. S. Ngwana argued, articulating the so-called Anglophone problem, parts of Cameroon spent nearly fifty years – between 1916 and 1959 – under different colonial administrations, absorbing different cultures and modes of governance.

[14] Their central role in the regional economy provoked escalating xenophobia among Cameroonian residents, an "Igbo scare" which after the Second World War was harnessed to nationalist local politics.

[20] The peninsula, located in the Gulf of Guinea between the Rio del Rey and Cross River State, was strategically important to both countries, both for its access to the port of Calabar – which housed the Eastern Command of the Nigerian Navy, as well as Nigeria's Export-Processing Zone – and for its oil resources.

[23] In the period of warm bilateral relations following the Nigerian civil war, border talks under the Joint Nigeria–Cameroon Frontier Commission intensified, resulting in the signature of the 1975 Maroua Declaration, which delimited the maritime boundary between Cameroon and Nigeria and recognised Cameroonian sovereignty over Bakassi.

[28] Although Nigeria initially protested the decision, and although it caused significant unrest in Bakassi, Olusegun Obasanjo's regime largely cooperated with the ruling.

"[31] At the request of Biya and Obasanjo, UN Secretary-General Kofi Annan established the Cameroon–Nigeria Mixed Commission to negotiate a smooth implementation of the International Court of Justice's 2002 ruling.

The commission's responsibilities included demarcating the entirety of the Cameroon–Nigeria border, facilitating cross-border cooperation and troop withdrawals from Bakassi, and protecting the rights of locals.

[32] After 2010, however, the insurgency spilled over from Nigeria into the Lake Chad basin, including the underdeveloped Far North of Cameroon, which has served as a recruitment ground for Boko Haram, as well as a refuge from Nigerian security services.

[36] Cross-border livestock theft has also increased: the World Bank estimates that, between 2013 and 2018, Boko Haram stole from Cameroonians at least 17,000 heads of cattle (worth around US$6 million) for sale in Nigeria.