The 'Long 1990s' is the period between the annulment of the 12 June 1993 presidential election and the swearing-in of Olusegun Obasanjo on 29 May 1999 — five-and-a-half years during which Nigeria was governed by Ibrahim Babangida's collapsing transition, Ernest Shonekan's three-month Interim National Government, and from 17 November 1993, by the regime of General Sani Abacha. It is the most concentrated period of state violence, censorship and exile in the country's post-civil-war history.
Within weeks of seizing power Abacha dissolved the National Assembly, the elected state governors and the local government councils, banned the two parties Babangida had created, and ruled by decree through the Provisional Ruling Council. Decree 2 of 1984 (detention without trial) and Decree 4 of 1984 (offences against the regime) were re-activated and supplemented by Decree 12 of 1994 ('treasonable offences'), Decree 14 (proscription of The Guardian, Concord and Punch), and the notorious Decree 24 (the Constitution Suspension and Modification Decree). The Civil Liberties Organisation, the Constitutional Rights Project and Human Rights Watch documented at least 1,000 political detentions in 1994–98 alone.
On 11 June 1994 MKO Abiola declared himself President at Epetedo, Lagos; he was arrested on 23 June 1994 and held without trial in Aguda House, Abuja, until his death in custody on 7 July 1998. The National Democratic Coalition (NADECO) was formed at the Lagos Airport Hotel on 15 May 1994 — its founders included Anthony Enahoro, Adekunle Ajasin, Bola Ige, Bola Tinubu, Olu Falae, Cornelius Adebayo, Wole Soyinka, Beko Ransome-Kuti and Pa Abraham Adesanya — to demand the de-annulment of June 12 and the convocation of a Sovereign National Conference. Within a year most of its leaders were in exile (Soyinka, Tinubu, Enahoro, Ajasin, Adebayo, Falae's deputy Ralph Obioha) or in detention (Adesanya, Ige, Beko, Ndubuisi Kanu).
The regime responded with assassination. Alfred Rewane, NADECO financier, was murdered in his Ikeja home on 6 October 1995. Kudirat Abiola, Abiola's senior wife and the public face of the June 12 movement, was shot dead in her car on Oregun Road, Lagos on 4 June 1996; Major Hamza Al-Mustapha, Abacha's Chief Security Officer, and Sergeant Barnabas Jabila ('Sergeant Rogers') were tried and convicted (later acquitted on appeal in 2013) for the killing. There were assassination attempts on Abraham Adesanya (14 January 1997, he survived because the bullets did not pierce his car door), on Alex Ibru, publisher of The Guardian (2 February 1996, he survived with severe injuries), on the journalist Bagauda Kaltho (disappeared March 1996, never found), and the killing of Suliat Adedeji (14 November 1996). The Oputa Panel later named state actors in each case.
The Ogoni movement of Ken Saro-Wiwa, organised through MOSOP, was crushed in the same period: Saro-Wiwa and eight co-defendants were hanged at Port Harcourt Prison on 10 November 1995 after a trial by special military tribunal that the Commonwealth, the UN, the EU and every credible jurist denounced. Nigeria was suspended from the Commonwealth on 11 November 1995; oil sanctions were debated and never imposed.
The phantom 'coup' trials — Obasanjo, Yar'Adua, Beko Ransome-Kuti, Shehu Musa Yar'Adua's group in March 1995, and the 'Diya coup' of December 1997 — produced more than 40 death sentences (later commuted) and led to the death in custody of Major-General Shehu Musa Yar'Adua at Abakaliki Prison on 8 December 1997, almost certainly by poisoned injection.
The resistance was sustained from abroad. Radio Kudirat, broadcast clandestinely from Norway via short-wave from December 1996, became the most-listened pirate station in West Africa. The exile groups around Soyinka (United Democratic Front of Nigeria, UDFN) and the NADECO Abroad offices in Washington, London, Toronto and Accra ran the international lobbying that produced US Executive Order 13088 (sanctions on Abacha personally), Canadian and EU travel bans, and a sustained press campaign that made Abacha synonymous with kleptocracy. The Pius Okigbo Panel, set up by Abacha himself in 1994 to look into the management of $12.4 billion of Gulf War windfall receipts under Babangida, found that the money had been spent 'neither in the National Budget nor for any identifiable public purpose' — a finding the regime suppressed.
The end came suddenly. Abacha died in Aso Rock in the early hours of 8 June 1998 — officially of a heart attack, popularly believed to have been poisoned by apples served by two Indian prostitutes flown in by his security detail. Abdulsalami Abubakar succeeded him within 24 hours, released the political detainees over the following month, and announced a one-year transition. Abiola died on 7 July 1998 in the presence of US Under-Secretary Thomas Pickering and UN envoy Kofi Annan, hours before his planned release — also of a 'heart attack' that the subsequent (and inconclusive) Patterson autopsy could neither confirm nor disprove. The transition produced the 1999 Constitution (promulgated by Decree 24 of 5 May 1999, never put to referendum) and Obasanjo's election on 27 February 1999. The Long 1990s ended at noon on 29 May 1999.