Another factor is the Pentagon’s relative insulation from politics, which has allowed it to sustain a long-term research agenda in controversial areas. No matter which party is in power, the Pentagon has continued to invest in clean-energy technology, for example, in an effort to find ways to reduce one of its largest budget items, energy costs.

The looming Defense Department cuts come from two sources. The Obama administration, as part of its deficit-reduction plan, has committed to cut military spending by $450 billion over the next decade. And the failure of Congress to agree on a plan for deficit reduction by a November deadline triggered a law requiring another $500 billion in Pentagon cuts over the next decade, starting in 2013. The combined effect would cut the Pentagon’s planned 2013 budget by 17 percent.President Obama outlined his vision Thursday for the first round of cuts, saying that military needs to become leaner and more technologically sophisticated. And military leaders say that they have embraced the necessity of a smaller budget. But they continue to warn that the second round of cuts would go too far. The defense secretary, Leon E. Panetta, in increasingly strident public remarks, has warned that the cuts would leave behind a “hollow military.” And he and others have warned of grave consequences for the economy.

Military spending does not compare well economically with many other forms of government spending, some experts say. Professor Pollin calculated in a recent analysis that $1 billion in spending on health care produced an economic benefit about 14 percent larger than spending on defense. The impact of spending on transportation, education and energy were even larger.

A recent study of federal spending since World War II by Alan Auerbach and Yuriy Gorodnichenko, both economists at the University of California, Berkeley, found that the economic benefits from nonmilitary spending were at least 50 percent larger than those from defense spending during periods of normal growth.

Some economists, however, argue that such studies fail to account for the economic value of security and stability. The crucial benefit is not what defense spending provides but what it prevents, Joshua Aizenman, a professor of economics at the University of California, Santa Cruz, and Reuven Glick, a researcher at the Federal Reserve Bank of San Francisco, wrote in a 2006 paper.

Other analysts see reasons that Defense Department cuts might cause disproportionate pain. Military contractors may struggle to find new customers for highly specialized products and services. And rank-and-file military personnel may struggle to find jobs. The unemployment rate for recent veterans was 13.1 percent in December, while the overall rate dropped to 8.5 percent, according to the Bureau of Labor Statistics.

On the flip side, some scientists say the military’s record of research success is unlikely to continue.