The indictment and resignation of I. Lewis 'Scooter" Libby yesterday deprives the White House of one of its most influential national security thinkers, a powerful advocate for some of the Bush administration's most far-reaching foreign policy decisions since the terrorist attacks of Sept. 11, 2001.

His pending legal battle, however, could also bring new scrutiny to the actions of the close-knit group of officials, many of them his old friends and colleagues from previous Republican administrations, who had long agitated for overthrowing Saddam Hussein and who are accused of exaggerating the threat from Iraq to achieve their goal, according to current and former government officials and specialists.

As the point man in the seat of power for the so-called neoconservatives, Libby was perfectly suited to carry their message: In 1992, as a senior Pentagon official, he coauthored a secret military blueprint asserting that the United States must 'act independently when collective action cannot be orchestrated" to protect its interests by force. The draft document was never approved, but had a key word -- 'preempt" -- that became synonymous with a more aggressive, unilateral US foreign policy.

A decade later, as chief of staff and Vice President Dick Cheney's national security adviser, Libby persuaded President Bush and Cheney, his boss, to adopt a strategy of preemptive war in Iraq, arguing inside the White House on behalf of like-minded allies such as former deputy secretary of defense Paul D. Wolfowitz, former undersecretary of defense Douglas J. Feith, and former undersecretary of state John Bolton. Feith has left government service, Wolfowitz is now head of the World Bank, and Bolton is the US ambassador to the United Nations.

Unlike previous vice presidential aides, Libby participated in the highest White House war councils, granted access usually reserved only for the president, vice president, Cabinet secretaries, and the national security adviser. White House aides and former government officials say the powerful team of advisers he assembled around Cheney in early 2001 at times eclipsed the influence of the National Security Council, the primary policy-making body. Libby also played a critical role in crafting the administration's sales pitch justifying the invasion of Iraq to remove its suspected weapons programs, including acting as a source for reporters.

Frank Gaffney, a former assistant secretary of defense in the Reagan administration who has known Libby for years, predicted yesterday that opponents of the war and US foreign policy critics will use Libby's legal jeopardy to put the neoconservatives in the Bush administration under a harsh spotlight.

'By all accounts, Libby was one of a very small number of advisers included in the meetings. Does that make him the bogeyman, the fall guy, the critical individual in how the war has been decided?" he asked. 'Not necessarily."

But opponents 'will seize upon this just the same," he said.

Libby is considered a charter member of the neoconservative movement, a collection of current and former government officials and foreign policy intellectuals -- some say idealists -- who believe that America's best defense is a muscular, military-based foreign policy used to spread democratic ideals, by force and without international allies if necessary.

As a Yale undergraduate in the early 1970s, Libby first became a protege of Wolfowitz, then a Yale professor who is now considered the dean of the neoconservatives and the top architect of the Iraq war. He then followed Wolfowitz to Washington, first in the State Department during the Reagan years and later at the Pentagon during the presidency of George H. W. Bush, when Cheney was defense secretary.

Throughout the 1990s Libby -- along with Wolfowitz, Feith, Cheney, Secretary of Defense Donald H. Rumsfeld, and a slew of other leading defense and foreign policy officials -- clamored to finish the job they failed to complete in the 1991 Persian Gulf War: removing Saddam Hussein as the first step to installing Western-style democracy throughout the Middle East.

In the late 1990s, Libby was among those associated with the Project for a New American Century, a think tank that publicly urged President Clinton to use military force to remove Hussein from power.

When Wolfowitz became Rumsfeld's top deputy at the Pentagon in early 2001, Cheney asked Libby to be his right-hand man in the White House.

'If you go back to the early days immediately after the result of the 2000 election was ratified, you see an extremely experienced team with a certain set of views," said Jonathan Clarke, a senior fellow at the libertarian CATO Institute and coauthor of 'America Alone," a history of the neoconservative movement.

'You had a group of people with very substantial experience in government and had worked together before and had really deep networks around Washington. It was an unusual and Libby was the pivot."