BELFAST, Northern Ireland — Bitter enemies from Northern Ireland’s bloody past joined forces yesterday atop a new Northern Ireland government, a once-unimaginable achievement that both sides pledged would consign decades of death and destruction to history.The bombastic Protestant evangelist Ian Paisley, long known as “Dr. No” for his refusal to compromise with the Roman Catholic minority, formed an administration with Sinn Fein deputy leader Martin McGuinness, a veteran commander in the outlawed Irish Republican Army, which long dreamed of wiping Northern Ireland from the map.

Their long-polarised parties will jointly run a 12-member administration that took control of the territory’s government departments from Britain. Their new shared goals: improve hospitals, schools, roads and other services and co-operate with the neighbouring Republic of Ireland.

Power-sharing was the central goal of the US-brokered Good Friday accord of 1998, a pact rejected by Paisley’s Democratic Unionist Party at the time because it included Sinn Fein. Britain and Ireland toiled to bring the factions together after 2003, when voters made them the dominant parties in the Northern Ireland Assembly, the foundation stone for co-operation.

Paisley’s conversion to compromise became possible because the IRA finally convinced him it would no longer try to oust Northern Ireland from the United Kingdom by force. The IRA renounced violence and disarmed in 2005, has not been implicated in significant violence since, and this year agreed with its Sinn Fein allies to accept the authority of the Northern Ireland police.

British Prime Minister Tony Blair, who made brokering peace a top priority since rising to power in 1997, paid particular tribute to Paisley — noting his stubborn stand had forced the Sinn Fein-IRA movement to go farther than many thought possible.

“I lost count of how many times I was told he would never accept sharing power,” Blair said of Paisley. “But he told me, in the right circumstances, that he would. He said he wanted to see Northern Ireland at peace and would not flinch from doing what was necessary to get that peace — on the only terms that he thought would endure. I believed him, and he has been true to his word.”

Even though all of Northern Ireland knew for weeks this day was coming, it still stunned observers to see Paisley, 81, and McGuinness, 56, smiling beside each other alongside Blair and Irish Prime Minister Bertie Ahern.

Paisley shared the amazement.

“If you had told me some time ago that I would be standing here to take this office, I would have been totally unbelieving,” Paisley told a crowd of jubilant, even giddy politicians and other dignitaries, including US Sen. Ted Kennedy, packed into the lobby of Stormont Parliamentary Building.

Paisley, who leads his own fire-and-brimstone church as well as a political party, mined the wisdom of the Old Testament’s King Solomon, who held that societies inevitably face a time of war and of peace, of hate and of healing.

“From the depths of my heart, I believe Northern Ireland has come to a time of peace, a time when hate will no longer rule,” Paisley said. “How good it will be to be part of a wonderful healing in this province. Today we have begun the work of planting, and we will all look for the great and blessed harvest.”

McGuinness, renowned as an organiser but not for oratorical flair, said the road ahead for Northern Ireland will bring “many twists and turns. It is however a road which we have chosen.”

Turning to Paisley, McGuinness wished his new partner “the best as we step forward towards the greatest and most exciting challenge of our lives.”

Back in the 1960s headwaters of the sectarian conflict, Northern Ireland was governed exclusively by Protestants — and Catholics were demanding equal rights in housing, jobs and the vote. Extremists on both sides opted for violence.

Paisley, dismissed in those days by most Protestant politicians as a lunatic bigot, led Protestant mobs against Catholic marchers, while his hate-filled speeches fanned support for outlawed Protestant paramilitary groups.

He spent time in prison for organising illegal protests, but rebounded to build a Protestant party, the Democratic Unionists, that campaigned on a promise to “smash Sinn Fein.” He was known for thundering “Not an inch!”, “No surrender!” and “Never!” when urged to compromise.

McGuinness, a high school dropout and apprentice butcher, joined a revived IRA that developed new tactics, particularly car bombs, to ravage Northern Ireland and reduce the territory to near-anarchy in the early 1970s, the bloodiest years.

He spent three years in prison for IRA membership, but emerged to become a senior commander committed to making the IRA an unbreakable force of small, secretive cells.

Throughout the conflict, about 3,700 people died and tens of thousands were maimed in Northern Ireland, England and the Irish Republic before Sinn Fein leader Gerry Adams, McGuinness and other senior IRA figures persuaded the underground organisation to cease fire in 1997.

The Good Friday accord of 1998, supported by Sinn Fein even though it contained a target for the IRA to disarm by mid-2000, foresaw a future of compromise centred on Protestants and Catholics sharing power. It assumed traditional moderate parties would stay solidly in the majority.

But when the IRA initially refused to surrender any of its Libyan-supplied arsenal, Protestant support faded for Nobel Peace Prize laureate David Trimble, the Protestant pragmatist who led power-sharing, and toward Paisley, who decried the Good Friday pact for conceding too much to Sinn Fein.

A 2003 election for the Northern Ireland Assembly produced twin triumphs for Paisley and Sinn Fein, a seemingly impossible combination.

But Blair and Ahern coaxed the two sides together in a seemingly endless series of summits, bluntly telling Sinn Fein leaders they must meet Paisley’s demand for a cast-iron end to the IRA. Eventually, it happened to Paisley’s satisfaction.

With the IRA fading away and Sinn Fein helping govern part of the United Kingdom, Blair — who is expected to announce his retirement from office this week — called on the crowd to remember the horrors of Northern Ireland’s yesteryears.

“We need to remember what it was like — to marvel at how it was changed,” he said.