Defense Secretary Robert Gates said that the United States' military needs to prepare to for the threats of "smaller, irregular forces" that have spurred on military conflicts in the past 25 years.

In a speech at the Heritage Foundation on Tuesday, Gates said that another major American conventional ground operation is unlikely in the near-future.

"[I]t is hard to conceive of any country confronting the United States directly in conventional terms -- ship to ship, fighter to fighter, tank to tank -- for some time to come," he said. "The record of the past quarter century is clear: the Soviets in Afghanistan, the Israelis in Lebanon, the United States in Somalia, Afghanistan, and Iraq. Smaller, irregular forces -- insurgents, guerrillas, terrorists -- will find ways, as they always have, to frustrate and neutralize the advantages of larger, regular militaries."

Gates added that the United States has strength in its Navy and Air Force, which can defeat "any -- repeat, any -- adversary who committed an act of aggression."
"It is true that we would be hard-pressed to launch a major conventional ground operation elsewhere in the world at this time - but where would we sensibly do that?" he said.

Gates welcomed more scrutiny of military spending, especially when money is used for war and not to modernize forces.

"First, I believe that any major weapons program, in order to remain viable, will have to show some utility and relevance to the kind of irregular campaigns that, as I mentioned, are most likely to engage America's military in the coming decades," he said.

He said that programs such as the Army's Future Combat Systems, which calls for a group of manned and unmanned forces working together, must demonstrate its value for the "irregular challenges" the country will face to justify its cost, which could exceed $200 billion.