Sinn Fein members overwhelmingly voted Sunday to begin cooperating with the Northern Ireland police, a long-unthinkable commitment that could spur the return of a Catholic-Protestant administration for the British territory.
The result _ confirmed by a sea of raised hands but no formally recorded vote _ meant Sinn Fein, once a hard-left party committed to a socialist revolution, has abandoned its decades-old hostility to law and order.
The vote, taken after daylong debate among 2,000 Sinn Fein stalwarts, represented a stunning triumph for Sinn Fein chief Gerry Adams, the former Irish Republican Army commander who has spent 24 years edging his IRA-linked party away from terror and towards compromise.
It strongly improved the chances of reviving power-sharing, the long-elusive goal of the 1998 Good Friday peace pact, by Britain's deadline of March 26.
"The decision we have taken today is truly historic," Adams told the conference after receiving a thunderous standing ovation at the Royal Dublin Society conference center. "Its significance will be in how we use this decision to move our struggle forward. Today you have created the potential to change the political landscape on this island forever."
Earlier, many speakers said for decades they had dreamed of defeating the province's mostly Protestant police force and forcing Northern Ireland into the Irish Republic.
Some IRA veterans recalled beatings inflicted on them by detectives during interrogations. Others noted they had served long prison sentences for attacks on police, more than 300 of whom were killed during the IRA's failed 1970-1997 campaign.
But nearly all speakers said they were voting, however reluctantly, to dump their party's anti-police position for the sake of peace.
"This shows that the war is over. And if the war is over, we have to build the peace," Adams said in an interview during an earlier break in debate.
Other Sinn Fein leaders sought to cloak their historic U-turn in bellicose terms, arguing that their position as the major Catholic-backed party in Northern Ireland meant they would be able to tell police commanders what to do.
"We have to boss policing, because we are the bosses," said Sinn Fein deputy leader Martin McGuinness, who according to police and the Irish government was an IRA commander from the early 1970s until last year.
McGuinness said the expected strong "yes" vote to policing wouldn't mean people in Sinn Fein power bases should be expected to welcome police into their communities.
"They're going to have to earn our trust. And we will let them know that they are going to be the servants of the people, not the other way around," McGuinness said.
At stake is the revival of power-sharing, the central goal of the U.S.-brokered Good Friday peace accord of 1998. A previous coalition collapsed in 2002 amid chronic Protestant-Sinn Fein infighting over the IRA's future.
Since then the Democratic Unionists, who represent most of the province's British Protestant majority, have insisted they will form a Cabinet alongside Sinn Fein only if Adams' party demonstrates support for law and order in areas where, from 1970 to 2005, justice often was administered with IRA bullets to the legs of petty criminals.
Crucially, however, the party motion approved Sunday commits Sinn Fein to begin supporting the police only after power-sharing is revived _ and only if the Democratic Unionists agree to transfer control of Northern Ireland's justice system, including the police, from Britain to local hands by May 2008.
Such conditions are likely to mean further protracted arguments with the Democratic Unionists, who are refusing to make either commitment until they see Sinn Fein's behavior to the police change.
Nonetheless, Sunday represented the first time since 1998, following the Good Friday pact, that Sinn Fein's grass-roots members were even asked to approve the next stage of painful compromise. By contrast, other key commitments _ particularly the IRA's 1994 and 1997 cease-fires, and its 2005 decisions to declare the truce permanent and to surrender its weapons stockpiles _ were products of years of secret diplomacy.
In London, British Prime Minister Tony Blair said Sinn Fein's policing shift would be only the start of a critical period in peacemaking.
"The next few weeks will be as important as the negotiation of the original Good Friday agreement," Blair said.
"We will determine whether we have a basis for the future in Northern Ireland, that allows us to have power-sharing ... on a solid basis for the first time ever," said Blair, who has made brokering compromise with Sinn Fein a major goal since rising to power a decade ago.
Chief Constable Hugh Orde, commander of the Police Service of Northern Ireland, said IRA supporters no longer had any valid reason to withhold support for his force, which is midway through a mammoth 10-year reform program as part of the Good Friday deal.
The reform effort, which already has boosted Catholic officers from 8 percent to 20 percent of the force, meant people in Sinn Fein strongholds should feel free to telephone police when they see crimes happening. Orde said he also expected people to cooperate when police come into Catholic areas to investigate.
"We have a right to say that, if this vote goes in the right direction, we need to see some tangible outcome," he said.