The annual confrontation involving the Protestants of the Orange Order brotherhood and the Catholics of Portadown's Garvaghy Road district triggered widespread violence from 1996 to 1998, the first year that a British-appointed Parades Commission enforced a ban on the Protestants from parading past the Catholic homes.
Since then, Orange Order leaders in Portadown, a principal power base for the anti-Catholic fraternal group, have maintained their stubborn refusal to negotiate directly with the Catholic protesters.
But in a telling sign that attitudes are slowly changing, a former top Orange figure in Portadown, David Burrows, this year joined the Parades Commission that upheld the restrictions and renewed its call for the Protestant side to negotiate.
As in previous years, the commission has ordered police to block the parade from leaving an Anglican church on a hilltop called Drumcree and heading down nearby Garvaghy Road back into Portadown.
The Orangemen refuse to take a different, longer route through predominantly Protestant areas, citing their right to freedom of assembly.
Unlike previous years, police erected no steel barricade on the narrow country lane outside the church on Saturday.
Alan Todd, Craigavon District Commander, the commander overseeing Sunday's security operation, said his force was prepared for trouble, including the use of two massive mobile water cannons, if necessary, but didn't expect any.
Protestants rioted for four days and nights, blocking roads and shutting down Northern Ireland's main airport, when police first tried to block the parade in 1996.
Police caved in to the pressure, permitting the parade down Garvaghy Road, and triggering three more nights of Catholic rioting across this British territory.
Similarly intense Catholic rioting followed the 1997 surprise decision by the police to flood the Garvaghy Road with British troops and force the parade down the thoroughfare.