The attack that killed Qusay and Uday Hussein could set off an immediate wave of retribution attacks, officials said, but the deaths should also embolden more Iraqis to come forward with critical information to energize the American military's antiguerrilla operations.

Evidence of the deaths, the officials said, will allow them to make the most convincing case that senior leaders of the Hussein government would never return to power — and that Iraqis need no longer fear openly supporting the United States.

Before today, Defense Secretary Donald H. Rumsfeld routinely cited the climate of fear imposed by Mr. Hussein over the decades of his rule as a significant brake on efforts to pacify and rebuild Iraq. Mr. Hussein's sons served as his two most senior advisers and their survival at the very least helped inspire the insurgency.

"Key regime figures had spheres of influence, and many in Uday and Qusay's spheres of influence are without a doubt sleeping better tonight," said James R. Wilkinson, spokesman for the United States Central Command in Tampa, Fla.

But the top prize — Saddam Hussein — remained elusive, and initial reports on the attack included no indication of whether information might have been seized at the house to point to his location.

Even so, the raid raised hopes among military officials in Iraq and at the Pentagon that they were tightening the noose around Mr. Hussein himself. A senior military official said the Pentagon would learn more about the kind of hiding places Mr. Hussein and his former top aides may be using. The second floor house in Mosul was so heavily fortified that it took missiles fired from either Apache or Kiowa helicopters to blast it open so troops could enter.

The attack may also validate arguments by senior American commanders who have resisted calls from some lawmakers and other critics to increase the number of troops on the ground in Iraq from the current level of 148,000, saying better intelligence combined with fast-acting troops is the answer.

In an interview on Sunday, Gen. John P. Abizaid, the commander of American forces in the Persian Gulf, described a scenario that foreshadowed the raid today.

"It's not a matter of boots per square meter," General Abizaid said. "It's a matter of focused intelligence, and then troops that are agile enough to carry out missions in a manner that can cause surprise and take down the targets precisely."

The military has conducted hundreds of raids over the past few weeks, not to seize hundreds of fighters but to confiscate huge caches of weapons and hoards of cash, gold and jewels meant to finance a long-term guerrilla resistance.

American officials were particularly hopeful that the deaths would lead more Iraqi informants to come forward. Since President Bush declared an end to major combat on May 1, American forces have relied heavily on tips from such informants and from insurgents captured in a running series of raids, to hunt down an elusive array of Baath Party diehards, foreign guerrilla fighters and terrorists.

"We've seen an increase in informants coming forward to our military, to our intelligence people and to our police in the last three weeks, and this is an obvious example of a culmination of that," said L. Paul Bremer III, the senior American occupation administrator, after briefing lawmakers on Capitol Hill today. "I would hope this will encourage other Iraqis to come forward."

Lt. Gen. Ricardo S. Sanchez, the American ground commander in Iraq, told reporters in Baghdad that the developments will enhance the allies' credibility with Iraqis, some of whom have questioned whether the United States was secretly holding Mr. Hussein, and possibly his sons, to ensure Iraqis dis what they were told.

General Sanchez said, "We remain totally committed to the Hussein regime never returning to power and tormenting the Iraqi people."

Judith Yaphe, an Iraq specialist at the National Defense University, said that "even those who have shown the most loyalty to the regime, and thought it could survive or come back, can't be putting much hope on Saddam's returning if his sons are not alive."

News of the two sons' deaths, she said, "is not going to stop all of the attacks against us." But, she added, "it could weaken, it could lower the degree of them." She cautioned, though, that "there are going to be some people who are going to be cranky no matter who is alive or dead, because they have nothing to lose."

One Bush administration official said tonight that the United States carried the burden of proving to the Iraqi people, and indeed to the Arab world at large, that the two sons were actually dead, and that Pentagon efforts to produce evidence of Mr. Hussein's brutality to his own people would continue.

General Sanchez acknowledged that providing public proof was essential, and promised to provide more details at a televised briefing in Baghdad on Wednesday.

Deputy Defense Secretary Paul D. Wolfowitz told reporters on Monday, after completing a five-day trip to Iraq, that the allied public information campaign must do a better job of promoting the occupation's accomplishments and debunking the guerrilla propaganda.

The mission today may also have a positive effect far beyond quieting the resistance, because it could serve as a big morale boost for the soldiers who have lived, fought and patrolled in the desert for months.

In fact, while Pentagon officials cautioned that they had only preliminary reports from the battle, one military officer briefed on the mission said Apache helicopters flown by the 101st Airborne had performed admirably, which could polish an image of the choppers that some say was tarnished early in the war.

In late March, when army aviation mounted its first attack on Republican Guard forces, the Apaches of the 11th Aviation Regiment were surprised by an Iraqi tactic of throwing up a wall of small-arms fire that downed one helicopter and damaged more than two dozen others.

Missions like the one conducted today often call up the fearsome AC-130 gunship, an Air Force Special Operations plane that carries aloft heavy machine guns and cannon, but the Apache received the assignment for close-air support today and did well, military officials said.

That Mr. Hussein's two sons could elude 160,000 troops for so long begs the question of whether it was the $15 million reward on each son's head that inspired the betrayal, or something else.

American intelligence officials say Mr. Hussein's former secretary told interrogators that the Iraqi leader split from his two sons on April 10. Uday and an aide fled to Syria, but were forced back into Iraq. Saddam Hussein was not believed to have been at the site of the raid. 

"It's only a matter of time before we find Saddam Hussein," Mr. Bremer said, "and I hope that day is a day earlier now."