On 17 January 1983, four months before President Shehu Shagari faced re-election against Chief Obafemi Awolowo, his administration announced that all 'illegal aliens' had two weeks to regularise their status or leave the country. The Internal Affairs Minister Ali Baba, the Justice Minister Richard Akinjide (SAN), and the Lagos State Commissioner of Police executed the order with a federal show of force at the land borders and at Murtala Muhammed International Airport.
An estimated 2 million people — by far the largest group Ghanaian, but also Togolese, Beninois, Nigerien, Chadian, Cameroonian and Liberian — left in a fortnight. Photographs of the exodus at Seme (Lagos–Benin Republic border) and along the Lagos–Sokoto–Birnin Kebbi corridor became the era's defining images: families on foot or in lorry beds, possessions stuffed into cheap chequered plastic-weave laundry bags. The bag itself — manufactured in China and Taiwan and sold across West African markets in the 1970s — was renamed 'Ghana Must Go' overnight and has carried that name into Nigerian English permanently. (It has since acquired a second, sardonic, political meaning — bagged cash distributed at party conventions.)
The immediate trigger was the collapse of oil prices from late 1981 and the corresponding collapse of the labour market in Lagos, Port Harcourt and Warri, where Ghanaian teachers, technicians, fishermen and traders had filled posts created by the 1970s boom. The deeper context was the 1969 Aliens Compliance Order of Ghana, under which Prime Minister Kofi Busia had expelled around 200,000 Nigerians (and others) from Ghana — Nigerians have, in the Shagari telling, returned the favour.
The expulsion was widely criticised abroad and contributed to the diplomatic isolation of the Shagari administration in its final months. A second wave of expulsions followed in May 1985 under the Buhari military government, smaller in scale but identical in method. ECOWAS's Protocol on Free Movement of Persons (1979), to which Nigeria was a signatory, was never formally suspended but was honoured in the breach.