THE August day 43 years ago when soldiers kicked in doors at dawn and took 342 men and boys away to undisclosed destinations triggered powerful emotion and remembrance in northern nationalists.
But that was a long time ago. Now Internment Day has multiple meanings, for most unionists probably nothing more than that it still makes nationalists boil with anger.
More likely, Catholic reactions are varied: to the original drama and its aftermath, then the anniversaries, marked for decades by riots, and now to the 21st century version.
A challenging work in progress, black leather jackets, tough middle-aged faces, jeering marchers in Royal Avenue matching jeering loyalists on the footpath: not pretty, hardly fitting. Present-day Sinn Fein want no bonfires and none of the finger-gestures, like at least some dissidents. The organisers of Sunday's march to the centre of Belfast seemed fairly focused on holding today's mainstream republicans up to ridicule.
But, going by the look of it, the strongest motivation was probably the urge to remind the loyal orders that the city belongs to nationalists too. Putting it up to the police to protect them was a by-product.
Some may have been impelled to march by what internment and its aftermath did to their own families but it was hard to see dignified remembrance.
The footpath catcallers had even less dignity. Stuck between fireworks, random thrown objects and mutual bile the PSNI looked stoical: do the marchers give them any credit?
As for the weekend's messy bonfires, the mainly juvenile arsonists may have had no more in their heads than a date that used to mean community-wide disorder, generally sanctioned: where's their fun?
The majority of today's young Protestants almost certainly know nothing about internment except the word, probably not even that. For most of those in the unionist community old enough to have lived through it, it was probably little more than
an early Troubles "security initiative". Probably most nationalists know that almost 2,000 were interned for considerable periods. They certainly know the total included a scant hundred suspected or actual loyalists.
Then, as later, arrests of loyalists left many unionists cold, like the imbalance. Protest about disregard for habeas corpus had no traction outside nationalism.
There was, if anything, a unionist expectation that police had been keeping tabs for decades on the shrinking world of physical force republicanism. But the RUC Special Branch was well outpaced by the fast developing Provisional IRA, their files out of date and plain wrong. Many Catholics well know, though few Protestants, that more than a hundred of the first detainees were released inside two days, with most
of the 2,400 arrested in the next six months similarly freed after a short time. Stormont prime minister Brian Faulkner recorded that British Home Secretary Reginald Maudling said to him "lift some Protestants if you can"
The then-British ambassador to Dublin Sir John Peck wrote later that internment, blatantly one-sided, attacked the Catholic community as a whole.
Even before the "inhuman and degrading treatment" of experimental interrogation techniques used on a group of the first internees became known, people unengaged until then blazed with the sense of injustice. Few in the other community understood.
A few years ago Sir Kenneth Bloomfield, who went on to head the civil service, told a BBC anniversary documentary internment had "succeeded on previous occasions" but in 1971 "it soon became clear that far from quelling the uprising, the policy hugely increased recruitment into the IRA".
Faulkner at the time was sure it was working because "we hear the squeal of the increasingly cornered rat". He was wrong on that, as on the internment decision, Bloomfield's "uprising" fitted ill with what had existed before Internment Day, but the sense of injustice certainly brought the IRA recruits.
That long-ago August 9 began with massive interruption of many lives, followed by widespread gunfire. Panicky flight in short order saw more than 2,000 families leave their homes.
The 1971 death toll until August 9 was 31. By the end of the month 35 more had died, 13 on the ninth alone: a 14-year-old, two 50-year-old women, a priest trying to give the Last Rites, a 19-year-old British soldier, the first UDR man to be shot. Internment Day in Ballymurphy became a 72-hour marathon.
Giving bystanders the fingers hardly measures up to all that sorrow.