"We knew he had them, we knew we would find them. It was just a matter of time," said an exultant Mr. Bush, who has been subjected to constant criticism for more than a year over the failure to find the WMD that sparked the invasion of Iraq in April 2003.

Bush said a covert military intelligence team discovered the arsenal in an underground fortress 10 miles west of the city of Anah. The stockpile included artillery shells and long-range missiles loaded with anthrax, nerve gas, VX, sarin and other deadly toxins. The team also found extensive laboratories where fatal poisons were being developed which could be used in smaller-scale terrorist attacks, such as in subways, airports, even city water supplies.

"It was like the gates of hell had been opened," Bush said. "These weapons and toxins could have destroyed hundreds of thousands of innocent lives, all around the world. Today has been a triumph of good over pure evil, and another ringing testament to America’s greatness." 

Bush said the weapons and the laboratories have been completely destroyed, to avoid any of the material falling into the wrong hands.

"These instruments of evil have been obliterated and scattered to the four winds," the president said. "No trace of them remains. Let this be a lesson to all those who would raise their hands against the peace and security of humankind: they will be wiped from the face of the earth."

Administration officials said that pictures of the operation will probably be released in the coming days, after being carefully vetted to avoid disclosure of any vital security information, including the identities of the secret military intelligence team.

White House officials said the discovery was the result of painstaking intelligence work. A senior official with direct knowledge of the operation said that "much of the actionable intelligence" had been garnered from the "strenuous interrogation" of Iraqi prisoners being held in Abu Ghraib prison. The discovery comes just days after news reports on alleged prisoner abuse by U.S. personnel at Abu Ghraib – allegations which threatened to become a major scandal, and perhaps an obstacle to Mr. Bush’s chances for re-election in the fall.

But today’s news will likely sweep away such concerns, along with the lingering doubts over the existence of Iraq’s WMD, and the resulting discontent with a war that has proven more difficult to end than most people expected. The crowds that spontaneously appeared outside the White House and at Ground Zero in New York to cheer the news seemed to bear out this analysis.

"He was right all along, he was right to invade, he was right to treat these prisoners like the animals they are," said Sandra Lucas, a day-care teacher from Baltimore who came to the White House to celebrate.

"You gotta do what it takes to get the job done," said Ken Mahafalous, a stockbroker who joined the Ground Zero crowd. "If it takes a war to keep us safe, if it takes a little rough stuff now and then, that’s what you do. I admit I had my doubts – and I didn’t vote for Bush in the first place – but this is real leadership, making the tough calls. My hat’s off to him. USA! USA!"

There was wide bipartisan praise for the operation and for Mr. Bush’s "gutsy" call in launching the war and persevering with the occupation despite the doubts and the criticism. The few dissenting voices were swiftly rebuked for "politicizing" a moment of national unity. Sen. Ross Feingold (D-WI) was widely denounced for his skeptical comments after Bush’s announcement.

"They destroyed all evidence of the weapons as soon as they found them in a top-secret operation? That doesn’t make sense to me," Feingold said in an interview with NBC’s Tim Russert. "Now no one else can independently confirm what actually happened. We are supposed to take the administration’s word at face value – no questions asked. I’m not saying the weapons weren’t there, but force-feeding a docile public with unconfirmable statements – especially about matters which have been swathed in murk and mystery for years – this is not the way a democracy is supposed to work."

Feingold’s remarks drew the ire of prominent commentators such as Parton Digby.

"I expect this from a Neanderthal drunk in a bar today, but coming from a US Senator it's enough to make you sick," Digby wrote. "But I think Feingold’s motives are probably fairly prosaic. He’s up for re-election and wants to shore up his antiwar cred among the fringe left. The moonbats are in desperate need of a fresh conspiracy theory and this one has the potential to be a doozy. I mean, why else would anyone ever express the slightest skepticism about our government’s covert actions? You either have to be crazy, or else pushing some partisan agenda. Or maybe both."

Although the discovery and destruction of Iraq’s WMD was the aim of the 2003 invasion, President Bush made it clear that the war will go on.

"We are not yet safe from those who hate us for our freedoms and our way of life," said Mr. Bush. "We must in fact redouble our efforts to ensure the safety of our children and bring democracy and stability to these volatile swamps of extremism. And we can expect our enemies to strike back even harder in response to our triumph today. But to them, I say: bring it on. For we are America. And America can do whatever we set our mind to."