Police took an Irish flag from a Belfast window, and the Falls Road erupted

On the morning of Sept. 28, 1964, a group of heavily armed policemen smashed down the door of a small election office on the Lower Falls Road in Catholic West Belfast and walked out carrying an Irish tricolor.

Outside, about 2,000 people had gathered to watch. They jeered, threw stones, and pressed in as the officers carried the flag away.

What happened over a piece of cloth became the heaviest street violence in Northern Ireland in more than 30 years, a moment when the later conflict may have begun. By the time it ended, rioters had thrown stones and gasoline bombs and torched a trolley bus, hundreds of policemen with batons, armored cars, and water cannons had cleared the Falls Road by force, and 50 civilians and 18 policemen were in the hospital.

The flag belonged to Liam Macmillan, a former fighter in the Irish Republican Army's failed border campaign who was running as an independent Republican in Britain's general election for Parliament. He had hung the large green, white, and orange flag in the window of his campaign headquarters.

That was enough to trigger a law. Under the Flags and Emblems Act of 1954, passed by the Protestant-controlled parliament at Stormont, the Royal Ulster Constabulary, Northern Ireland's overwhelmingly Protestant police force, could remove any flag thought likely to cause a breach of the peace. The law was aimed at the Irish flag, though in practice police usually left it alone when it flew inside Catholic neighborhoods.

Ian Paisley would not leave it alone. At a rally he declared, "I do not accept that any part of Ulster is Republican. I do not want to see the tricolour flying here." Under that pressure, the police decided to act.

The seizure lit the fuse. Thousands battled police in West Belfast. When news reached Dublin, a crowd gathered outside the British Embassy, throwing stones until Irish police held them back. It was the first time since the war that London papers had almost noticed the province. The Times wrote that there was "a sickening familiarity about all of this."

Paisley counted it as a win. The flag had come down, his name was in the papers, and he could present himself as the defender of Protestant Ulster. Two weeks later, when Unionist Jim Kilfedder won the West Belfast seat, he publicly thanked Paisley for his support.