WASHINGTON -- In roughly eight hours of often heated discussions with the Senate Armed Services Committee Thursday, defense secretary-nominee Chuck Hagel raised and then left unanswered the critical question looming over the Pentagon: with defense budgets sinking, should U.S. defense strategy shrink as well?

And no one on the committee bothered to ask, with more than $1 trillion scheduled to be whacked out of the Pentagon's 10-year spending plan, what missions will it give up? Which parts of the world should go unpatrolled, which allies unsupported, which brush-fire conflicts allowed to burn on untended?

Those questions took on added urgency as Hagel, a former Republican senator, described a world of continuing danger, with challenges from nuclear-armed North Korea, terrorism-sponsoring Iran, turmoil across the Middle East and North Africa, a well-armed and restive China, cyber war, al Qaeda, war in Afghanistan, extremist violence in nuclear-armed Pakistan, piracy and other problems.

"We're at war around the world," Hagel testified.

But as he also acknowledged, "This is a time of priorities. Budgets drive that, but missions should always drive everything. What are going to be our missions in the Defense Department over the next few years? How are we going to resource those missions, what are the priorities going to be?" What's up for rethinking, he said, "is the entire universe of what the [national security] responsibilities are and how we carry those responsibilities out to secure this nation."

As some members leaned forward to hear him outline his own ideas on a revised strategy, Hagel concluded, "Until I would get over to the Pentagon, if I am confirmed … I won't be in a position to say this or this or we'll do this or we won't."

Rather than probing deeper into Hagel's ideas about how U.S. defense strategy could be revised, many of the committee members' questions involved Hagel's past positions on Israel, Iran and whether the "surge" of troops into Iraq in 2007 worked or didn't.

But the Pentagon's fiscal outlook is well known. After a decade of fat and rising budgets, it is now facing deep cuts and an era of relative austerity. It will lose $45 billion out of its operating budget in the remaining eight months of this fiscal year if automatic budget cuts known as sequestration go into effect March 1, as scheduled.

The Obama administration has already deleted $487 billion from the Pentagon's 10-year budget plan, erasing a planned increase. Another $500 billion will be drained out of the Pentagon's accounts over the next 10 years under congressional budget agreements.

The immediate effects are startling. Two of the Navy's carrier battle groups, which are scheduled to deploy this fall, would be delayed for as long as nine months as the Navy absorbs a $4.6 billion shortfall in its operations budgets this year. That means turbulent areas like the Persian Gulf and the South China Sea could go without the presence of U.S. naval power. Thirty of the Navy's 187 surface warships are due in for extended overhauls this year, work that would have to be postponed, Adm. Jonathan Greenert, chief of naval operations, said recently.

The military services have already been ordered to cut personnel over the next few years. The Army will shrink by 80,000, from 570,000 to 490,000 soldiers, and the Marine Corps will lose 67,000 Marines, bringing its strength down to 182,000. And given the continuing budget pressure, many expect further manpower cuts.

Those and other cuts carve deeply into the Pentagon's ability to continue its operations as currently planned, Hagel acknowledged in his written answers to the Armed Services Committee.

"The current strategy," he wrote, "could not be met with the significantly diminished resources that sequester would impose," including "the grounding of aircraft and returning ships to port, reducing the Department's global presence and ability to rapidly respond to contingencies."

The Pentagon, he added will "need to revise the defense strategy."

But he gave no hint of what that revision would look like.

Only one member of the committee, freshman Sen. Deb Fischer (R-Neb.) observed that the impending budget cuts will leave the Defense Department unable to respond to the challenges Hagel had described. "How do you decide what is going to be the priority?" she asked.

"I hope I did not give any indication we were going to be able to continue to do everything for everybody everywhere," Hagel responded late Thursday afternoon. "If I am confirmed, I will be working closely with our chiefs and all of our managers and decision-makers on how we do this."

The lack of a strategy underpinning the looming defense cuts worries some outside analysts. "I am quite alarmed that we seem to be in the middle of all kinds of budget deliberations without first starting with what we are trying to do as a nation," John Hamre, the former Pentagon comptroller and deputy defense secretary, said recently at an event sponsored by the Center for Strategic and International Studies, the Washington think tank where Hamre is president and CEO.

"Looking ahead," he said, "we ought to have a firm view of what it is we need to do, not just how much money are we going to have."

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  • Chuck Hagel (February 2013 - Present)

    New Secretary of Defense Chuck Hagel is greeted as he arrives for his first day at the Department of Defense, on February 27, 2013 in Arlington, Va. (Photo by Drew Angerer/Getty Images)

  • Leon Panetta (July 2011 - February 2013)

    Secretary of Defense Leon E. Panetta pauses while speaking during a ceremonial swearing-in at the Department of Defense July 22, 2011 in Washington. (Source: <a href="http://www.defense.gov/specials/secdef_histories/">Department of Defense</a>)

  • Robert Gates (Dec. 2006 - July 2011)

    Robert Gates speaks during his ceremonial swearing in as the 22nd defense secretary on Dec. 18, 2006 at the Pentagon. (Source: <a href="http://www.defense.gov/specials/secdef_histories/">Department of Defense</a>)

  • Donald Rumsfeld (Jan. 2001 - Dec. 2006)

    U.S. Secretary of Defense Donald Rumsfeld holds his press conference at the Pentagon briefing room on Jan. 26, 2001 in Arlington, Va. (Source: <a href="http://www.defense.gov/specials/secdef_histories/">Department of Defense</a>)

  • William Cohen (Jan. 1997 - Jan. 2001)

    Secretary of Defense designate William Cohen testifies during confirmation hearings before the Senate Armed Services Committee on Jan. 22, 1997 in Washington. (Source: <a href="http://www.defense.gov/specials/secdef_histories/">Department of Defense</a>)

  • William Perry (Feb. 1994 - Jan. 1997)

    U.S. Defense Secretary William Perry points to a reporter during a press conference on April 21, 1994 in Seoul, Korea. (Source: <a href="http://www.defense.gov/specials/secdef_histories/">Department of Defense</a>)

  • Les Aspin (Jan. 1993 - Feb. 1994)

    U.S. Secretary of Defense Les Aspin released new regulations governing gays in the military during a press on Dec. 22, 1993 at the Pentagon. (Source: <a href="http://www.defense.gov/specials/secdef_histories/">Department of Defense</a>)

  • Dick Cheney (March 1989 - Jan. 1993)

    U.S. Defense Secretary Dick Cheney (L) meets Egypt's President Hosni Mubarak, on April 3, 1989, at Washington. (Source: <a href="http://www.defense.gov/specials/secdef_histories/">Department of Defense</a>)

  • Frank Carlucci (Nov. 1987 - Jan. 1989)

    U.S. Defense Secretary Frank Carlucci testifies before the Senate Armed Services Committee on July 13, 1988 in Washington. (Source: <a href="http://www.defense.gov/specials/secdef_histories/">Department of Defense</a>)

  • Caspar Weinberger (Jan. 1981 - Nov. 1987)

    Caspar Weinberger, Secretary of Defense on Feb. 9, 1981. (Source: <a href="http://www.defense.gov/specials/secdef_histories/">Department of Defense</a>)

  • Harold Brown (Jan. 1977 - Jan. 1981)

    General Alexander M. Haig, right, retired as NATO commander, walks with Defense Secretary Harold Brown during an awards ceremony on July 3, 1979 at Fort Myer, Va. (Source: <a href="http://www.defense.gov/specials/secdef_histories/">Department of Defense</a>)

  • Donald Rumsfeld (Nov. 1975 - Jan. 1977)

    A 1976 photo of Secretary of Defense Donald Rumsfeld. (Source: <a href="http://www.defense.gov/specials/secdef_histories/">Department of Defense</a>)

  • James Schlesinger (July 1973 - Nov. 1975)

    Israeli Defense Minister Moshe Dayan, left, with Secretary of Defense James R. Schlesinger, chats on Friday, Jan. 5, 1974 at the Pentagon. (Source: <a href="http://www.defense.gov/specials/secdef_histories/">Department of Defense</a>)

  • Elliot Richardson (Jan. 1973 - May 1973)

    Elliot L. Richardson speaks to newsmen Oct. 23, 1973 at a press conference held at the Department of Justice. (Source: <a href="http://www.defense.gov/specials/secdef_histories/">Department of Defense</a>)

  • Melvin Laird (Jan. 1969 - Jan. 1973)

    Secretary of Defense Melvin R. Laird as he departed from Andrews Air Force Base Md., for Paris on Jan. 5, 1971 in Washington. (Source: <a href="http://www.defense.gov/specials/secdef_histories/">Department of Defense</a>)

  • Clark Clifford (March 1968 - Jan. 1969)

    This is an Oct. 1968 photo of Secretary of Defense Clark Clifford as he announces his support for President Johnson's decision to halt the bombing of North Vietnam. (Source: <a href="http://www.defense.gov/specials/secdef_histories/">Department of Defense</a>)

  • Robert McNamara (Jan. 1961 - Feb. 1968)

    PARIS, FRANCE: US Secretary of Defense Robert McNamara smiles as he arrives 27 November 1965 at Paris' NATO headquarters. (Source: <a href="http://www.defense.gov/specials/secdef_histories/">Department of Defense</a>)

  • Thomas Gates (Dec. 1959 - Jan. 1961)

    Secretary of Defense Thomas S. Gates Jr., center, poses with Benjamin M. McKelway, left, editor of the Washington Evening Star and President of the AP, and AP General Manager Frank J. Starzel at the April 25, 1960 meeting of the Associated Press in New York. (Source: <a href="http://www.defense.gov/specials/secdef_histories/">Department of Defense</a>)

  • Neil McElroy (Oct. 1957 - Dec. 1959)

    Defense Secretary Neil McElroy said he has "fullest confidence that the United States is ahead of the Soviets..." prior to the announcement of the Soviet's achievement in launching the first earth satellite, Oct. 4, 1958. (Source: <a href="http://www.defense.gov/specials/secdef_histories/">Department of Defense</a>)

  • Charles Wilson (Jan. 1953 - Oct. 1957)

    Charles E. Wilson, left, takes the oath of office from Chief Justice Fred Vinson at the White House in Washington on Dec. 21, 1950 as head of the office of Defense Mobilization. (Source: <a href="http://www.defense.gov/specials/secdef_histories/">Department of Defense</a>)

  • Robert Lovett (Sept. 1951 - Jan. 1953)

    Gen. Dwight D. Eisenhower (right) watches President Harry S. Truman and Gen. Omar Bradley help Defense Secretary Robert Lovett (left) get in place as the men posed on the south lawn of the White House on June 1, 1952 in Washington. (Source: <a href="http://www.defense.gov/specials/secdef_histories/">Department of Defense</a>)

  • George Marshall (Sept. 1950 - Sept. 1951)

    Anna M. Rosenberg, New York Labor and Public Relations consultant, who is named assistant secretary of defense, chats with Secretary of Defense George Marshall in a conference at the Pentagon on Nov. 9, 1950 in Arlington, Va. (Source: <a href="http://www.defense.gov/specials/secdef_histories/">Department of Defense</a>)

  • Louis Johnson (March 1949 - Sept. 1950)

    Defense Secretary Louis Johnson (right) gives new identification card to President Harry Truman at the White House on Nov. 9, 1949 in Washington, listing him as commander in chief for an "indefinite" term. (Source: <a href="http://www.defense.gov/specials/secdef_histories/">Department of Defense</a>)

  • James Forrestal (Sept. 1947 - March 1949)

    James V. Forrestal, Secretary of Defense under President Harry Truman, is shown on July 26, 1947. (Source: <a href="http://www.defense.gov/specials/secdef_histories/">Department of Defense</a>)