LONDON — It had been billed as a civil rights march to redress long-festering hurts, one among many that freckled Europe in the heady days a half-century ago when the streets from Paris to Prague became arenas of revolt.
But that particular protest in Northern Ireland on Oct. 5, 1968, signaled the beginning of something that endured for three decades, seeding an insurgency that became known with weary understatement as the Troubles.
From then until a settlement known as the Good Friday Agreement was signed in 1998, some 3,600 people died in conflict that had all the appearances of civil war, with roadblocks and bomb blasts, sniper fire and the suspension of civil rights.
The British authorities deployed the army against their own citizens in a province that had been carved out as a Protestant enclave at the partition of Ireland in 1921. Protest drawing on centuries of disaffection turned to armed revolt spearheaded by the underground Irish Republican Army and its political wing, Sinn Fein, which cast themselves as the most radical champions of an aggrieved Roman Catholic minority.
At the same time, loyalist paramilitary groups challenged the I.R.A., supposedly to protect a Protestant majority, fearful that any dilution of the bond with Britain might destroy its power and identity. Their activities injected one more element of violence into a war of many dimensions.
The conflict was not confined to the six counties that make up Northern Ireland. The I.R.A. drew significant support from groups as disparate as Irish-Americans in the United States and the Libyan dictator Muammar el-Qaddafi, who supplied significant amounts of arms and powerful explosives.
The bombings spread to the rest of Britain, targeting senior figures including Prime Minister Margaret Thatcher. Mortars were fired at 10 Downing Street, the prime minister’s official residence and office, and at Heathrow Airport outside London. British troops hunted down I.R.A. members as far afield as Gibraltar.
Even today, 20 years after the Good Friday Agreement brought a form of peace, low-level violence persists. Quasi-tribal divisions are preserved in huge murals on the gable ends of rowhouses, depicting each side’s heroes. A shared executive authority, set up as part of the 1998 accord, has been suspended since January 2017, because of intractable disputes between the main players — largely Protestant unionists seeking continued ties to Britain and mainly Catholic nationalists pressing for a united Ireland free of British control.
The Good Friday pact “cooled things down a bit,” said Paul Bew, a leading historian and emeritus professor at Queen’s University in Belfast. “But if you are talking about a shared view of history, in therapy terms it’s like an agreement between a husband and wife who still can’t stand each other but have to find a way to live together.”
Most ominously, the Northern Irish issue that preoccupied six British prime ministers from Harold Wilson to Tony Blair has interposed itself anew into the halting negotiations on Britain’s withdrawal from the European Union, expected to happen in just six months.
At the time of the Good Friday pact, Britain and Ireland were both members of the European Union, meaning that they could largely dismantle the border between Ireland and Northern Ireland in line with the bloc’s commitment to the free passage of goods, services and people among member nations. But a chaotic British withdrawal could scuttle that arrangement.
A so-called hard border would “require infrastructure that will damage economic and social ties along the border,” said Edward Burke, an international politics professor at Nottingham University in England who has written a book on the British Army’s campaign in Northern Ireland. “All the artfully created foundations of the agreement will be damaged.”
Such weighty considerations might have seemed remote on Oct. 5, 1968, though the harbingers of deepening division and rival narratives were already plain enough. Even the geography of the protest reflected the schism: Unionists called the town where the march took place Londonderry; nationalists called it Derry. Merely using the wrong term in the wrong place would invite hostility in the battle of emblems and perceptions that suffused and sustained the Troubles.
Some neighborhoods still remain segregated by so-called peace walls as high as 45 feet that keep mutually inimical communities apart.
“I think the Troubles cast a huge shadow today,” said Susan McKay, an author, journalist and documentary filmmaker from Londonderry. “The reality is that the areas from which a lot of the Troubles emanated — the poorest and most deprived parts of Northern Ireland — are still the poorest and most deprived parts of Northern Ireland. The children and grandchildren of those who participated in the Troubles the most are still scarred by them today.”
Fifty years ago, hundreds of nationalist protesters, gathered on Duke Street in Londonderry. Their demonstration, organized by the Northern Ireland Civil Rights Association — inspired in part by the civil rights movement in the United States — had been outlawed when unionist opponents announced plans for a rival march. The organizers resolved to protest anyhow, fired by a long-simmering discontent with what was perceived as widespread discrimination.
Suddenly, the terms of battle shifted. Officers from the Protestant-dominated police force — the Royal Ulster Constabulary — surrounded the demonstrators with batons drawn, cutting off lines of retreat. A water cannon sprayed the crowd.
One protester, Deirdre O’Doherty, told the BBC that she fled into a cafe as “police battered people left, right and center.” One officer burst in “with a baton in his hand with the blood dripping off it,” she said. “He was young. He looked vicious. I never saw a face with so much hatred in my life.”
As the strife deepened, the British Army was deployed.
In time, as the Troubles burgeoned, so, too, did the competing versions of what lay behind them. For many in Britain, who became stoically inured to the threat of I.R.A. bombings, it was about suppressing terrorism. For nationalists, it was a broader fight to throw off the yoke of colonialism and foreign oppression.
Northern Ireland’s heroes were often its martyrs. On Jan. 30, 1972, thousands of marchers, most of them Catholics, took to the streets of the Bogside district of Londonderry to display opposition to the new policy of internment without trial. British soldiers opened fire, killing 14 protesters, all of them Catholic.
The events became known as Bloody Sunday. An official British apology did not come until 2010, when Prime Minister David Cameron described the killings as “both unjustified and unjustifiable.”
Like other turning points in the Troubles, and in the propaganda war that was one of the era’s most striking features, “Bloody Sunday” became woven into the republican narrative, offsetting accusations that the I.R.A. was far more brutal in its tactics than the British Army.
The chronology of the Troubles offers a tally of bloody episodes leading to yet more carnage in a murky underground war of spies, hit men, summary executions and still unexplained disappearances.
In less than two weeks in March 1988, for instance, British Special Forces operatives killed three I.R.A. members in Gibraltar. When their funerals were held in Belfast’s Milltown Cemetery, a lone extremist from the loyalist side, Michael Stone, attacked the ceremony with pistols and grenades, killing three mourners — one of them an I.R.A. supporter — in front of camera crews, photographers and journalists covering the burial. Three days later, I.R.A. operatives seized two nonuniformed British Army corporals mistaken for loyalist gunmen at the funeral of one of those killed in Milltown Cemetery. The soldiers were beaten and shot to death.
Sometimes, the I.R.A. offered warnings of its intention to detonate explosives in Britain. In 1993, the group told the police that it planned to detonate a bomb in London’s financial district, but the explosion killed a news photographer and injured some 40 people.
But the campaign was not fought exclusively with bombs and bullets. In 1981, Bobby Sands, a jailed I.R.A. commander sentenced on firearms charges, drew global attention to a hunger strike by inmates in response to the withdrawal of their special status within the prison system. Already, by virtue of a since-repealed law that permitted prisoners to stand as electoral candidates, Mr. Sands had been voted into the British Parliament.
After 66 days without food, he died at the age of 27. His death drew broad international criticism of the British government for its handling of the hunger strike.
But Mrs. Thatcher, the prime minister at the time, remained resolute. “Mr. Sands was a convicted criminal,” she told Parliament in London. “He chose to take his own life. It was a choice that his organization did not allow to many of its victims.” Her remark was oddly prophetic.
In 1984, a long-delay time bomb in a hotel in Brighton, England, exploded as Mrs. Thatcher, its principal target, and many members of her Conservative Party elite were there for an annual conference. Mrs. Thatcher escaped unhurt, but five people were killed.
“Today we were unlucky,” the I.R.A. said in a statement, “but remember we only have to be lucky once. You will have to be lucky always. Give Ireland peace and there will be no more war.”
It was a reminder of the essentially asymmetric nature of a conflict that pitted a NATO army against insurgents and irregulars fueled by competing visions of destiny that have endured far beyond the formal silencing of their weapons.
Decades later, the Troubles “are so burned into our lives that they are part of our DNA,” said Monica McWilliams, a former civil rights marcher, peace activist and feminist leader. “They are with us every day — especially those of us who were bereaved. It’s a festering sore, because it’s never been dealt with.”
Ed O’Loughlin contributed reporting from Dublin.
Produced by Gaia Tripoli