WASHINGTON — Defeating the enemies of tomorrow — from rogue nations to terror networks — will require a balanced and nimble military that can coax or confound an adversary as well as it can crush one, Defense Secretary Gates said yesterday.

Speaking to a class at the National Defense University, Mr. Gates said the Pentagon must have a broad range of capabilities, but should not try to buy its way out of every problem.

Instead, he said that lessons learned in Iraq and Afghanistan show that the Defense Department must learn to move with more speed and agility to field needed weapons and equipment.

Rather than waiting for a 99% solution that will take years to develop, Mr. Gates said the often sluggish bureaucracy must be able to field a “75% solution in months” to defeat insurgencies.

As examples he pointed to the struggles to get to Iraq mine-resistant vehicles and effective countermeasures for deadly roadside bombs — efforts that stumbled along for months as more troops died before the countermeasures finally took hold.

Asked about the effects of the current economic crisis, Mr. Gates acknowledged that the significant increase in defense spending spurred by the wars in Iraq and Afghanistan is probably now over, and the Pentagon will be fortunate if future budgets keep pace with inflation.

Still, he said he believes the American government and its elected officials have learned their lesson and will avoid the kind of drastic budget cuts that followed previous military buildups for World War II, the Korean and Vietnam wars, and the Cold War.

“Experience is that ability to recognize a mistake when you make it again,” Mr. Gates said. “One would hope that the fifth time around that we’ve learned the lesson.”

He said the fact that “the world does remain a complicated and dangerous place is further incentive not to cut capabilities.”

With just four months to go before he — and the Bush administration — turn control of the country’s military over to a new team, Mr. Gates issued a broad call for a more realistic defense strategy.

The nation, he said, must be prepared to face an international environment that is more complex and unpredictable today than it has ever been.

Pointing to the recent Russian incursion into Georgia, Mr. Gates said America still must have the high-tech power to go toe-to-toe with superpowers like Russia and China that are ramping up their militaries.

“The images of Russian tanks rolling into the Republic of Georgia last month was a reminder that nation-states and their militaries do still matter,” Mr. Gates said.

In a landmark speech nearly a year ago, Gates said winning the war on terror will require more “soft power,” with government agencies and civilian groups using economic and political aid to bolster weak nations and battle insurgents.

Again yesterday he said wars are not won by military might alone. But when creating that arsenal of weapons, there must be a mix of high-end bombers, cyber-tactics and missile defense along with lower-end skills to train, communicate and build.

Mr. Gates also urged patience, saying it will take “quiet successes over a long time” to defeat extremists, and a key part of that will be the need to build up America’s friends by bolstering their governments and training their security forces.