His household goods had just been moved into the renovated residence of the vice chief of staff of the Army five weeks ago when Gen. George W. Casey Jr. received word that he was likely headed for a new assignment: commander of all U.S. forces in Iraq.

The sudden shift -- triggered by the prison abuse scandal, which upset an earlier plan to install a different new commander in Iraq -- has left Casey scrambling to prepare for the job.

Yesterday, at a congressional hearing on his nomination, the general deferred answers to a number of central questions about the Iraq mission.

Will he have enough U.S. troops to deal with the surging violence? How will he coordinate with Iraqi authorities after the transfer of limited authority next week? What role will private security contractors continue to play?

Casey promised to get back to Congress when his views are more informed by experience. A soft-spoken, genial officer accustomed to dealing with lawmakers, Casey is a respected figure on Capitol Hill, and senators appeared willing to cut him some slack until he takes up his new post. Several even sounded relieved that someone such as Casey was willing to take the assignment.

"I don't know of a tougher job in regards to our national security than the one you're assuming," Sen. Pat Roberts (R-Kan.) told him.

Sen. John McCain (R-Ariz.), citing the rising sophistication of the insurgency in Iraq and the inability so far of U.S. and Iraqi forces to secure the country's borders, impressed on Casey that the situation had reached "a very, very critical" moment. "Success or failure may be dictated by what happens in the next few months," McCain said.

He urged Casey to make his own assessment of troop levels and other needs "as quickly as possible." He cautioned against making promises that cannot be delivered, noting that statements by commanders this spring threatening to subdue the city of Fallujah or kill or capture the radical cleric Moqtada Sadr never came to pass.

Several senators also took the occasion to express frustration at what they said has been a lack of candor on the part of the Bush administration about events in Iraq. They voiced hope that Casey would give them what Sen. Carl M. Levin (D-Mich.), the ranking minority member, called "the unvarnished facts," even if it meant going against the administration's official line.

Casey was not an obvious choice for the Iraq job. Apart from a stint as a U.N. military observer in Cairo in 1981, the general has spent little time in the Middle East. He also has no combat experience.

But Casey receives high marks from many active and retired officers for his thoughtfulness, calm temperament and skill in dealing with Washington and international bureaucracies.

In an interview, Casey cited a lifelong interest in international affairs, stretching back to his undergraduate days at Georgetown University's School of Foreign Service in 1970. Time spent as a senior officer in the 1990s sorting out the international jumble in Bosnia and Kosovo has helped prepare him for the political complexities and military challenges of Iraq, he said.

More recent stints at the upper reaches of the Pentagon's Joint Staff and the Army have made him very comfortable dealing at the national level and have given him a good understanding of how to coordinate matters between the Pentagon and State Department, he added.

In preparing for Iraq, Casey said he has talked at length with Ambassador John D. Negroponte, who will be heading the U.S. Embassy in Baghdad.

"We have a strong feeling that this needs to be one team, one mission," Casey said.

As for his lack of combat experience, he said that did not concern him.

"I've learned how to think competitively and how to operate against a thinking enemy, and that has great carry-over into combat operations," Casey said.

Among the lessons he said he has learned commanding troops in the past is the need to clearly communicate goals and policies to subordinates. He also believes that "the guy in charge must do a lot of heavy lifting himself" and that soldiers should take a break now and then.

"You have to find time to read, sleep, exercise and think, because if you don't, you end up stale and with a short-term focus," he said.

Casey had not intended to make a career of the military. His father, Maj. Gen. George W. Casey Sr., died in a helicopter crash in Vietnam in 1970 -- the year Casey graduated from Georgetown.

Although Casey was commissioned a second lieutenant after graduation, he planned to stay in the Army two years before entering law school. A subsequent decision to extend his military duty for a year to attend airborne school took Casey to Germany, an experience he enjoyed. He has remained in the Army ever since.

As a four-star general, Casey will bring greater authority to the Baghdad assignment than the three-star officer he is replacing, Lt. Gen. Ricardo S. Sanchez. The move is intended partly to consolidate U.S. troops -- including Special Operations forces and the Iraq Survey Group, which has been hunting for weapons of mass destruction -- under one command. It also is meant to enable Gen. John P. Abizaid, head of U.S. Central Command, who has responsibility for all U.S. troops in the Middle East, to spend more time on other matters.

In testimony yesterday, Casey rejected the notion that U.S. troops in Iraq, after the handover of limited authority next week, would be shifting from an offensive to a defensive posture. "We have to maintain an offensive mind-set," he told the senators.

Casey said U.S. forces might try to adopt a lower profile, but he said he intends to keep them focused on obtaining intelligence about insurgents and engaged in carefully planned attacks.

He predicted that intensified efforts to train and equip Iraq's fledgling security forces should begin yielding visible results in a few months, adding that the new emphasis will be more on the quality of the forces, not the quantity.

Asked about a possible role for NATO forces, Casey said he would welcome their assistance in training Iraqi troops. What he needs most from the international community, he said, is a brigade-size force -- about 5,000 soldiers -- to ensure security for the U.N. mission charged with helping set up national elections next year.

Gen. George W. Casey Jr. testifies before the Senate Armed Services Committee during yesterday's confirmation hearing on his nomination to head U.S. forces in Iraq.