The Sunni and Shiite tribesmen had come from across Iraq to turn the page on the fratricidal violence that tore the country apart in the years after the 2003 U.S.-led invasion.
But as they met yesterday, an 18-year-old member of the tribe blew himself up, killing at least 23 people and providing a jarring reminder of the obstacles to reconciliation, even within one clan.
Some members of the Qarqouly tribe had not seen each other for more than six years and had hoped to revive old ties after weathering the religious extremism and sectarian fighting that divided Iraq and destroyed families and friendships.
"The tribe members were happy to see each other," said Faris Qarqouly, who lost a brother in the bombing. "We didn't expect to be attacked." While the number of Iraqi civilians killed diminished sharply in 2008, Sunni militants are still carrying out lethal bombings. In the run-up to the U.S. military's handing over control of the nation's security to Iraqi government forces Thursday, more than 70 people died in two bombings in Baghdad and another in the northern city of Kirkuk.
Yesterday, several hundred Qarqouly tribesmen had gathered in Youssifiyah, a rural, Sunni-dominated area south of Baghdad, christened the "Triangle of Death" in 2003 because of the car bombings, beheadings and kidnappings that began to occur regularly on the crucial road between the capital and the largely Shiite south.
But things changed beginning in mid-2007, when U.S. forces seeking to defeat such Islamist groups as Al-Qaida in Iraq forged alliances with Sunni tribesmen who had supported the insurgency.
Since then, Youssifiyah had become quiet enough that the head of the Qarqouly tribe, Sheik Mohammed Abdullah Saleh, invited the confederation to join him there in what would have been a "death wish invitation" only a year earlier. Saleh wanted the tribe's Shiite and Sunni members to find common ground, according to tribesmen who attended the meeting.
Some said the idea had been broached of forming a political bloc at the meeting. Mixed tribes are common in Iraq.
The tribal leader, whose confederation has more Sunnis than Shiites, did not suspect that one of his own relatives, a teenager named Amin Ahmed Qarqouly who sometimes slept at his house, would blow himself up as dozens of people were leaving, said Iraqi army Col. Akram Hamidawi.
Saleh, the head of Youssifiyah's Sons of Iraq, the official name for Sunni paramilitaries fighting al-Qaida in Iraq there, was not among the dead, according to relatives and Hamidawi.
Amin, who lived in the same neighborhood, had been considered unlikely to attack his immediate family. In a show of affection, Amin had referred to Saleh as his grandfather, according to Hamidawi.
Amin stopped by the house frequently enough that no one frisked him when he came in through the back entrance, where women had been cooking. His mother and sister were among those attending the party.
Amin's father left before his son's attack and was wanted for questioning, Hamidawi said.
Amin had belonged to the Sunni insurgency and had been jailed in 2007 for his involvement with a group associated with al-Qaida in Iraq that might have been involved in the kidnapping of four U.S. soldiers later found dead, Hamidawi said.
He was released six months ago after a year behind bars.
"Why did he do this? All of these people were his cousins, brothers, uncles," demanded Hamidawi, insisting that al-Qaida in Iraq had been defeated in his area.
The bombing resembled some attacks in Anbar province, once a hub of the Sunni insurgency, where clans have split, with some choosing to continue fighting alongside al-Qaida in Iraq and killing fellow tribesmen who partnered with the U.S. military.
The tragedy showed how vulnerable the country remains to suicide bombings in the crucial run-up to provincial elections at the end of the month.