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Defense Secretary Leon Panetta has warned that possible budget cuts triggered by the breakdown of the congresssional “supercommittee“ would have devastating consequences, but many skeptics question whether such dire predictions are an exaggeration.

If members of Congress cannot implement a contingency plan, the Pentagon would have to bear half of the $1.2 trillion in budget cuts. The cuts would begin in 2013, when the Congressional Budget Office estimates that the Defense Department would have to slash 10 percent, or about $550 billion, from its budget. Combined with the $450 billion worth of cuts already planned, that would amount to $1 trillion in the next decade.

After 10 years, the cuts would leave the United States with the smallest ground forces since 1940, a Navy fleet that would be the smallest since 1915 and the lowest number of fighters in the Air Force’s history, Panetta warned. The Pentagon would have to cancel acquisition programs such as the Army’s helicopter and ground vehicle modernization programs and the new Air Force bomber program, delay others, and reduce the fleet. Wartime funding would not be affected.

“The impacts of these cuts would be devastating for the department,” Panetta said in a letter to Sen. John McCain, R-Ariz., last week. It “would render most of our ship and construction projects unexecutable,” and “seriously damage other modernization efforts.”

The cuts would be a double-edged sword, experts say. On the one hand, they would force the Pentagon to look more closely at its budget, which has ballooned in recent years, and make much-needed changes in how it allocates taxpayer dollars. On the other hand, it could make the Defense Department less efficient in the short term.

“The cuts are not as draconian as you might expect, given the rhetoric, but they are serious nevertheless,” said Todd Harrison, a senior fellow at the Center for Strategic and Budgetary Assessments. “It’s not the depth of the cuts. It’s the abruptness with which they will occur.”

Instead of making “smart cuts,” such as reducing the number of bases and the number of military and civilian personnel, the Pentagon would be forced to make “quick cuts” right away, Harrison added. That would likely entail terminating or delaying acquisition programs, a move that could end up costing more money in the future.

The cuts would put the Defense Department’s budget at $472 billion, the same level as in 2007, a spending high for the Pentagon. If it remains at 2007 levels, U.S. military spending would be almost three times that of China, and $38 billion above average annual spending during the Cold War, points out Winslow Wheeler, director of the Straus Military Reform Project and the Center for Defense Information.

Citing these numbers, supporters of defense budget cuts say Panetta’s warnings are overblown and that sequestration would be beneficial because it will force a change in the Pentagon’s culture of unquestioned funding by Congress.

Since the Sept. 11 attacks, the department has added $1.3 trillion in its budget for the wars and $1 trillion for its base budget. But all the while, the Navy and Air Force fleets have gotten smaller, the forces are less trained and the equipment is, on average, older than what it was a decade ago, Wheeler said.

“It’s a very flush-with-money budget,” Wheeler said. “To call such a level of spending a ‘catastrophe,’ or ‘doomsday,’ is a failure of management and intellect every bit as complete as the political failure of the hapless Democrats and Republicans on the so-called supercommittee.”

“The party’s over,” Wheeler added. “The Department of Defense needs to start making informed, hard decisions and those managers who cannot operate in that environment need to be replaced.”

Despite the supercommittee’s failure, members of Congress have the power to enact changes that would lessen the impact on the Pentagon. They can delay implementation of sequestration or change the terms so that the Defense Department has to bear less of the budget cuts, but then that money would need to come from social programs.

Members of Congress are hesitant to implement Pentagon budget cuts, but given the stalemate and bipartisan wrangling, it remains unclear whether there will be an alternative. If history is a guide, the automatic budget cuts likely won’t go into effect. The two times sequestration has occurred, first in 1988 and then in 1990, the budget cuts were either reduced or ended by legislation.

Top Pentagon officials have “ratcheted up the rhetoric about what the defense cuts would mean to a level where they’re fairly confident that Congress won’t actually let it go into effect in 2013,” Harrison said. “They are not doing anything to plan for the contingency. … They are hoping there is a silver bullet that’s going solve everything for them. There’s no guarantee that that will happen.”