British planned to maintain and expand their supply of free high-quality oil from BiafraLand

The British planned to maintain and expand their supply of cheap high-quality oil from Nigeria. Therefore they placed a high priority on maintenance of oil extraction and refining operations. They backed the Federal Government, but when the war broke out cautioned them not to damage British oil installations in the East. These oilworks, under the control of Shell-BP Petroleum Development Company (jointly owned by Shell and British Petroleum), controlled 84% of Nigeria's 580,000 barrels per day. Two-thirds of this oil came from the Eastern region, and another third from the newly created Mid-West region. Two-fifths of all Nigerian oil ended up in Britain.

Shell-BP therefore considered carefully a request by the Federal Government that it not pay the royalties demanded by Biafra. Its lawyers advised that payment to Biafra would be appropriate if this government did in fact maintain law and order in the region in question. The British government advised that paying Biafra could undermine the goodwill of the Federal Government. However, the payment was made, resulting in a blockade on oil. Forced to choose a side, Shell-BP and the British government threw in their lot with the Federal Government in Lagos, apparently calculating that this side would be more likely to win the war. As the British High Commissioner in Lagos wrote to the Secretary of State for Commonwealth Affairs on 27 July 1967:

Ojukwu, even victorious, will not be in a strong position. He will require all the international help and recognition he can get. The Federal Government would be much better placed both internationally and internally. They would have a cast iron case for the severest treatment of a company which has subsidized a rebel, and I feel fairly convinced they would press their case to the lengths of cancelling the Company's concessions and nationalizing their installations. I conclude, therefore, if the company does change its mind and asks the British Government for advice, the best that could be given is for it to clamber hastily back on the Lagos side of the fence with cheque book at the ready."

Shell-BP took this advice. It continued to quietly support Nigeria through the rest of the war, in one case advancing a royalty of £5.5 million to fund the purchase of more British weapons.

During the war, Britain covertly supplied Nigeria with weapons and military intelligence and may have also helped it to hire mercenaries. After the decision was made to back Nigeria, the BBC oriented its reporting to favor this side. Supplies provided to the Federal Military Government included two vessels and 60 vehicles.

In Britain, the humanitarian campaign around Biafra began on 12 June 1968, with media coverage on ITV and in The Sun. The charities Oxfam and Save the Children Fund were soon deployed, with large sums of money at their disposal.

France

France provided weapons, mercenary fighters, and other assistance to Biafra and promoted its cause internationally, describing the situation as a genocide. Charles de Gaulle referred to "Biafra's just and noble cause". However, France did not recognize Biafra diplomatically. Through Pierre Laureys, France had apparently provided two B-26s, Alouette helicopters, and pilots. France supplied Biafra with captured German and Italian weapons from World War II, sans serial numbers, delivered as part of regular shipments to Côte d'Ivoire. France also sold Panhard armored vehicles to the Nigerian federal government.

French involvement in the war can be viewed in the context of its geopolitical strategy (Françafrique) and competition with the English in West Africa. Nigeria represented a base of British influence in the predominantly French-aligned area. France and Portugal used nearby countries in their sphere of influence, especially Côte d'Ivoire under President Félix Houphouët-Boigny, as waystations for shipments to Biafra. To some extent, also, France repeated its earlier policy from the Congo Crisis, when it supported the secession of the southern mining province Katanga.

Economically, France was significantly incentivized by oil drilling contracts for the Société Anonyme Française de Recherches et d'Exploitation de Pétrolières (SAFRAP), apparently arranged with Eastern Nigeria in advance of its secession from the Nigerian Federation. SAFRAP laid claim to 7% of the Nigerian petroleum supply. In the assessment of a CIA analyst in 1970, France's "support was actually given to a handful of Biafran bourgeoisie in return for the oil." Biafra, for its part, openly appreciated its relationship with France. Ojukwu suggested on 10 August 1967, that Biafra introduce compulsory French classes in secondary, technical and teacher training schools, in order to "benefit from the rich culture of the French-speaking world".

France led the way, internationally, for political support of Biafra. Portugal also sent weapons; Czechoslovakia sent weapons until its priorities were adjusted by the 1968 Soviet invasion. These transactions were arranged through the "Biafran Historical Research Centre" in Paris. French-aligned Gabon and Côte d'Ivoire recognized Biafra in May 1968. On 8 May 1968, De Gaulle personally contributed 30,000 francs to medicine purchases for the French Red Cross mission. Fairly widespread student-worker unrest diverted the government's attention only temporarily. The government declared an arms embargo but maintained arms shipments to Biafra under cover of humanitarian aid. In July the government redoubled its efforts to involve the public in a humanitarian approach to the conflict. Images of starving children and accusations of genocide filled French newspapers and television programs. Amidst this press blitz, on 31 July 1968, De Gaulle made an official statement in support of Biafra. Maurice Robert, head of Service de Documentation Extérieure et de Contre-Espionnage (SDECE, the French foreign intelligence service) African operations, wrote in 2004 that his agency supplied the press with details about the war and told them to use the word "genocide" in their reporting.

France declared "Biafra Week" on 11–17 March 1969, centered on a 2-franc raffle held by the French Red Cross. Soon after, de Gaulle terminated arms shipments, then resigned on 27 April 1969. Interim president Alain Poher fired General Jacques Foccart, the lead coordinator of France's Africa policy. Georges Pompidou re-hired Foccart and resumed support for Biafra, including cooperation with the South African secret service to import more weapons.