WASHINGTON – Undersecretary of Defense Douglas Feith yesterday announced he will resign this summer, marking the exit of one of the strongest supporters of the Iraq war within the Bush administration and a lightning rod of criticism for war critics at home and abroad.

In a statement to the press, Defense Secretary Rumsfeld said the no. 3 civilian at the Pentagon is “creative, well organized, and energetic, and he has earned the respect of civilian and military leaders across the government. Regrettably, he has decided to depart, and he will be missed.”

Mr. Feith’s friend and former boss in the Reagan administration, Richard Perle, told The New York Sun yesterday that Mr. Rumsfeld had asked him to stay. “By the time he leaves it will be four and a half years. I know that Secretary Rumsfeld wanted him to stay. His departure sometime in the summer has no implications for policy or ideology or anything of the sort,” Mr. Perle said.

The Pentagon’s news release yesterday said Mr. Feith was leaving his post for “personal and family reasons.” Mr. Perle said that didn’t surprise him: “He gets up every day at 4 a.m. and leaves the office at 7 p.m. He doesn’t have any time to spend with his four young children. And that is a relationship that is very important to him.”

The resignation was announced as Congress prepares to investigate a new Pentagon intelligence unit that may command secret special forces missions without the same degree of oversight that similar CIA operations have required in the past.

Mr. Feith was often at the center of the partisan squabbles that emerged after the president’s decision to invade Iraq. Shortly after September 11, 2001, Mr. Feith gave a small group of analysts the task of reassessing the CIA’s raw intelligence on state sponsors of terrorism and links to Al Qaeda. From this analytical exercise, the Pentagon’s talking points for midlevel officials were forged on the issue of links between Saddam Hussein and Al Qaeda.

The September 11 commission’s report released last summer found those links did not amount to an operational relationship. Many of his critics, particularly on Capitol Hill, said Mr. Feith injected poor intelligence into the interagency decision-making process.

Another report from the Senate Select Committee on Intelligence last summer found that a Pentagon analysis produced by the Office of Special Plans was largely ignored in both the National Intelligence Estimate and Secretary of State Powell’s presentation to the United Nations.

The issue came to a head on the eve of the presidential election, when Senator Levin, a Democrat from Michigan, released his own report accusing Mr. Feith of presenting his intelligence to the White House without the CIA’s consent. At the same time, how ever, the Senate intelligence panel found the CIA lacked good human sources in Iraq and chastised the agency for its poor assessment of Iraq’s weapons of mass destruction program.

Mr. Feith’s rivals within the administration also disliked him, according to Washington Post reporter Bob Woodward. In Mr. Woodward’s latest book, “A Plan of Attack,” Mr. Powell was quoted by an anonymous official as saying Mr. Feith’s analysts were the equivalent of a Gestapo. Mr. Feith’s father is a survivor of the Holocaust; Mr. Powell later apologized.

That book also detailed exchanges between Mr. Feith and the commander of the military’s Central Command, General Tommy Franks, over whether the Pentagon should have trained Iraqi forces to go into Iraq with coalition soldiers. To this day, one of the most pressing needs of the new Iraqi government is the lack of adequately trained Iraqi forces.

Mr. Feith’s power peaked before the second Gulf war in March 2003. Shortly after that, his intelligence responsibilities were transferred to the newly created post of undersecretary of defense for intelligence, which was filled by Stephen Cambone. Meanwhile responsibility for overseeing the reconstruction of Iraq was ceded from Mr. Feith’s office to the National Security Council.

“There was a debate at the beginning of the war within the government,” one Pentagon official said yesterday. “Feith wanted to empower the exile government formed in northern Iraq, but he was eventually outvoted. As soon as (chief of the Coalition Provisional Authority) Paul Bremer came in, the Department of Defense was largely ignored on policy issues,” relating to Iraq.

As Iraqis prepare to vote for the first time in national elections Sunday, Mr. Feith’s original position to avoid an occupation and establish an interim government of Iraqis may prove correct. The party of the selected interim prime minister, Iyad Allawi, is not expected to garner many votes. However, the slate that includes Ahmad Chalabi, the Iraqi exile supported early in the first administration by Mr. Feith, is likely to emerge as a top leader in the new assembly.

Among his charges, many regarded Mr. Feith as an ineffectual manager. “I don’t think that even many of his friends are sad to see him go,” an analyst who worked on Persian Gulf issues for Mr. Feith, Michael Rubin, told the Sun. “Sometimes having the right positions is not enough. Management can be just as important as ideology.”

Nonetheless, Mr. Rubin praised Mr. Feith as an “ideas man.” “The fact of the matter is that 9/11 proved that policy was no longer business as usual. It is hard to take on an elite, and Feith excelled in recasting foreign policy and questioning conventional wisdom.”

The announcement of Feith’s resignation is sure to spark speculation among many of Washington’s chattering class that his departure signals the greater fall of neoconservatives within the administration. Not only is Mr. Feith leaving, but a prominent State Department hawk, Undersecretary of State John Bolton, has so far not been offered a job.

The vice president of foreign and defense policy studies for the American Enterprise Institute, Danielle Pletka, said this is the wrong analysis. “People get confused,” she said. “Personnel come and personnel go, and what many refuse to recognize is that the president’s views are not shaped by his staff. The staff’s views are shaped by the president.”