One of the worst crimes in a year full of atrocities was 'Bloody Friday' - the simultaneous detonation of more than 20 PIRA bombs in Belfast - which claimed nine lives.
By March 1973, a new political initiative was being tabled by the British government. It outlined plans for a new Northern Ireland assembly, elected by proportional representation, and a government for the region in which Protestants and Catholics would share power
It also proposed the creation of a 'council of Ireland' that would give the Republic a role in Northern Ireland's affairs - directly confronting one of the unionists' greatest fears.
Remarkably, the new assembly elections in June 1973 produced a majority of pro-power sharing representatives, but they were set against a large minority of implacably anti-power sharing unionists.
Nonetheless, the 11 ministry power-sharing executive started work in January 1974. Of its many inherent weaknesses, perhaps the greatest was the exclusion of anti-power sharing representatives from the executive and from the negotiations for the Council of Ireland.
The Sunningdale Agreement (named after the town in Berkshire where the negotiations took place) had agreed a 14-member Council of Ireland. It terms were vague, but the agreement raised the possibility that the Republic could one day gain some decision-making powers in Northern Ireland.
Unionists were split by the agreement, and the forthcoming British general election of February 1974 gave the anti-Sunningdale bloc an ideal opportunity to derail the process.
'The agreement raised the possibility that the Republic could gain decision-making powers in Northern Ireland.'
Representing the election as a referendum on Sunningdale, anti-agreement unionist candidates won 11 of Northern Ireland's 12 parliamentary seats. It was a disaster for the pro-Sunningdale assembly, since it could no longer claim to represent public opinion.
Nonetheless, the British government refused to call new assembly elections, and on 14 May 1974, the assembly, perhaps rashly, restated its support for Sunningdale. As a result, the Ulster Workers' Council - a coalition of Protestant trade unionists - called a general strike in the province later that same day.
Then on 17 May, loyalist bombs exploded in Dublin and Monaghan, ultimately claiming the lives of 32 people in the worst single outrage of the Troubles.
Within two weeks the shutdown had become total, with roadblocks, power-outages and a near-complete cessation of industry. The British government, now led by Harold Wilson, seemed unwilling to engage in this new and potentially crippling confrontation.
Indeed, Wilson's accusation that the strikers were 'sponging off Westminster' only helped galvanise support for the UWC.
On 28 May, the pro-Sunningdale unionist members of the power-sharing executive took the matter out of Wilson's hands. They resigned and direct rule was immediately reintroduced. It would last for another 25 years.