Was Obama's defense budget proposal provoked by a careful rethinking of military strategy, or primarily  by a desire to trim the federal deficit?

The important part of this process is that the strategy come first," White House spokesman Jay Carney said on Jan. 3.

In February 2010, when the Pentagon announced a new military strategy after a year-long study, then-Secretary of Defense Robert Gates called it an "important and historic" account of how the Pentagon would spend its money for at least the next four years. That study explicitly foresaw the winding down of the conflict in Iraq. So the Defense Department - despite abundant outside criticism of its review -- considered its strategy and spending levels set.

The study results nonetheless became rubbish the following year, because of intense political debate about the size of the deficit. In his signature April 2011 speech on the deficit, Obama promised a variety of savings, gave Gates a pat on the back for cutting a total of $400 billion in "wasteful spending," and then said "I believe we can do that again." He also backhanded the study, by calling for a "fundamental review of America's missions, capabilities, and our role in a changing world" - as if one had not just been done.

Gates was not informed of Obama's proposal - which was meant to be implemented over a dozen years -- until a day or so before it was made, according to officials involved in the process. White House officials now say they did not tell Gates earlier because he was traveling overseas and they wanted to convey the news in person.

But a former senior defense official privy to key deliberations says the White House provided no earlier heads-up because the idea came "out of thin air.... There was no logic, no strategy, no evaluation." The Pentagon was "not looking to find another $400 billion in cuts" and so it was simply left out of the loop, the official added.

"There was not a big plan put together" before the April announcement, an OMB official confirmed. But Obama was not taking numbers "out of the sky," the official said, since independent groups had earlier recommended much steeper defense spending cuts.

Since OMB director Jack Lew - the incoming White House chief of staff - and other top administration officials favored an even larger, faster budget cut, Obama's initial proposal to cut another $400 billion over a dozen years was changed by the White House, after an argument with the Pentagon, to $487 billion over ten years.

So, in summary, the administration's second strategic review, which started in April 2011 and ended on January 5, was not motivated by the Defense Department's conviction that it was time for a new direction.

It was instead an effort by the military service chiefs to decide which missions they still wanted to accomplish after Obama and his top national security advisers decided - as part of their new economic  policies -- to shoehorn the Pentagon's decade-long spending plan, estimated to cost around $6.25 trillion, into a box roughly 7 percent smaller.

What about something called "budget sequestration"? Isn't that going to make these numbers change a lot anyway?

Sequestration, according to the dictionary's definition, involves holding something temporarily  - like members of a jury or the property of a defendant -- before letting it go.

Many pundits and policymakers in Washington are nonetheless agitated about the prospect that the Pentagon will be forced to cut up to $500 billion beyond what Obama has proposed, as the result of a "sequestration" deal with Congress that requires spending reductions throughout the government unless certain deficit targets are met.

This would essentially reduce the Pentagon's current budget by about 16 percent in the year 2021. As the Stimson Center has pointed out, such a trim is comparable to shaving just three-quarters of one percent from the defense budget annually - in absolute dollars, not including inflation - from 2013 to 2021.

The fears over sequestration come from the bluntness of the scalpel: The deal would require the Pentagon to distribute the additional cuts equally among its major program categories, although it would still retain some discretion within those categories. Spending on Afghanistan would be exempt and Obama could also exempt military personnel if he chooses. But Panetta would not have the liberty of choosing to preserve or increase funding for the overall tasks he considers most important.

This restriction could be changed by Congress, and the sequestration itself can be reversed if Congress wishes to do so before it takes effect in January 2013. While many Republican lawmakers have threatened to undo the sequestration deal, Obama has promised to veto such plans, and the Republicans don't appear to have the votes to override such a veto.

Nonetheless, few who follow defense spending closely expect the defense budget to be deeply cut by sequestration. Asked how he plans to carry out the requirement, Panetta told an audience at Ft. Bliss, Texas, on January 12, "I'm not planning to do it at all."

One reason for ignoring the threat is that the defense industry is likely to block it. In 2011 alone, more than a thousand defense and aerospace lobbyists spent $46.6 million to influence Congress, according to an estimate by the nonprofit Center for Responsive Politics. The industry also gave lawmakers $22.7 million for the 2010 elections, and it has already contributed another $8.5 million to influence the election outcome in 2012.

Also, key Democrats have said their ambition, in striking the sequestration deal, was never to cut defense spending bluntly. Instead, they sought to draw on the industry's powerful influence to pressure Republicans into accepting a tax increase on the wealthy that would lift the threat of sequestration. For instance, Sen. Armed Services committee chairman Carl Levin, a Democrat from Michigan, has complained that sequestration would be highly damaging. But as he said on November 7, "I don't want to take the pressure off to reach a deal by talking about avoiding or eliminating the effects of sequestration."

Is that the end of the story, or will the defense budget be changed more than Obama has proposed, anyway, even without sequestration?

While standing next to Panetta on January 5, Army Gen. Martin E. Dempsey, the Joint Chiefs of Staff chairman, signaled that he knows 2012 is just the beginning of a new era for the military's budget. He called the department's new strategy "about right, for today."

Industry officials and independent experts say two political factors will likely provoke more cuts in the years ahead: First, Republicans are no longer united behind high military spending. The party is divided between national security hawks and deficit hawks, including many Tea Party members supportive of shrinking military as well as non-military spending. Second, as the overall budget shrinks, Democrats will regard defense spending as a competitor with social programs they wish to protect.

Gordon Adams, a Stimson Center expert and former Office of Management and Budget assistant director, said he expects a total cut of $1 trillion to $1.5 trillion over the next decade. "This is, after all, the lowest level of existential threat we have ever faced," said Adams, who helped oversee part of the 31 percent  cut in national security spending between 1986 and 1998. "Barring an attack by the ghost of Bin Laden on New York city, this is inevitable."

The bipartisan National Commission on Fiscal Responsibility and Reform, popularly known as the Bowles-Simpson commission, said in December 2010 that the United States needs to trim the overall federal deficit by $4 trillion by 2020 to avoid impeding economic growth. The deep budget cuts required to avoid sequestration - including defense spending changes double the amount proposed by Obama -- would only do half the job. So the pressure to make deeper defense cuts will not disappear anytime soon.

Obama's national security spending plan does not cut the defense budget. Even if his proposal is enacted, U.S. defense spending will continue to dwarf the rest of the world's. The new U.S. military strategy was concocted to accommodate the proposed budget trims, not vice versa. Sequestration is a threat, not a promise. And no matter what politicians say or do this year, U.S. defense spending will remain vulnerable to real cuts. The important question in the years ahead is, which military programs will survive and which will go away.

This article was published in partnership with the Center for Public Integrity.