The more than 2,600 traditional, Protestant marches that take place in Northern Ireland are at the core of unionism and loyalism.
The parades take place from Easter until September. Orange Order members, wearing bowler hats and orange sashes, walk through the streets of almost every town carrying large banners. They are often accompanied by pipe or flute bands.
Parades on 12 July every year are the biggest of the so-called marching season. They celebrate the victory of the Protestant Prince William of Orange over the Catholic King James II at the Battle of the Boyne in July 1690. The River Boyne is near Drogheda in the Republic of Ireland.
Orangemen say it is the single most important event at the core of the Ulster loyalist identity.
"We are not here to play games," said the Rev Ian Paisley during the 1996 stand-off over the contentious Drumcree march. "We are here to save Ulster. If the parade doesn't go down Garvaghy Road there will be civil commotion to an extent the authorities cannot handle."
There certainly has been violence. A stand-off between Orange Order members and police blocking access to the mainly nationalist Garvaghy Road, which is part of the traditional parade route, led to disturbances across Northern Ireland. In 1998, three young brothers were burned alive when a petrol bomb hit their house in what police said was a sectarian attack.
But even without violence, the parades are perceived by many in the nationalist community as a threat.
According to academics Neil Jarman and Dominic Bryan who published a recent report on parade culture: "Each parade which is challenged is a symbolic threat to Protestant security and the Unionist position. Each parade that passes through a nationalist area is a restatement of the dominance of the Protestant community and the inferiority of nationalist rights."
It is not an assessment with which unionists would agree. They reject claims of triumphalism. But in Northern Ireland perceptions often matter more than anything else.