From 1970 the Provisional Irish Republican Army was carrying out an armed campaign aimed ultimately at bringing about a united Ireland . As well as attacking military and political targets , it also bombed infrastructure and commercial targets in Northern Ireland and England . It believed that by damaging the economy and causing severe disruption , it could pressure the British government to negotiate a withdrawal from Northern Ireland . Manchester had been the target of earlier IRA bombs . Firebombs damaged city centre businesses in 1973 and 1974 , for which a man was later imprisoned . In April 1974 , a bomb exploded at Manchester Magistrates ' Court , injuring twelve . In 1975 , IRA bomb factories were found in Greater Manchester and five men were imprisoned for planning attacks in North West England . On 4 December 1992 , the IRA detonated two small bombs in Manchester city centre , forcing police to evacuate thousands of shoppers . More than 60 were hurt by shattered glass and the blasts cost an estimated £ 10 million in damage and business losses
detonated two small bombs
1992 Manchester bombing
1996 Manchester bombing