Some of the U.S. Army's sharpest minds warned young combat leaders of what they should expect as America enters a new chapter in its war with Islamic extremists.

Seasoned leaders such as retired Army Gen. Stanley McChrystal met with young Army officers and sergeants at Fort Benning, Ga., just hours before President Obama outlined his strategy for destroying the extremist group known as the Islamic State of Iraq and the Levant.

"We are at a period where our enemies respect us, but they don't fear us," McChrystal told his audience at the 2014 Maneuver Conference Wednesday. McChrystal is the former commander of U.S. and allied forces in Afghanistan.

"The specter of American power is no longer enough to get somebody just not to do something."

The United States will lead a broad coalition to "downgrade and destroy" ISIL in what will be a comprehensive and sustained counter-terrorism strategy, Obama announced Wednesday night.

Obama said he would approve the expansion of airstrikes into Syria.

"I will not hesitate to take action against ISIL in Syria, as well as in Iraq," Obama said. "This is a core principle of my presidency - if you threaten America, you will find no safe haven."

Obama assured the U.S. public that the effort will not include large numbers of combat troops on the ground.

But senior military officials see this as only the beginning. Lt. Gen. Michael Flynn, the outgoing head of the U.S. Defense Intelligence Agency, told the same group of young leaders that extremist groups such as ISIL - also known as the Islamic State of Syria and Iraq (ISIS) - and al Qaeda are expanding their cause to southeast Asia and other regions of the world.

"This is expansion; this is Bangladesh, Burma, Thailand, Cambodia, Laos and particularly Indonesia," Flynn said. "This is a big problem; it is well beyond ISIS. We are in a state of perpetual conflict. We are not post war force."

The U.S. military has an enormous amount of combat experience, but senior leaders' message to young combat leaders is they should not rely on this experience too much. U.S. soldiers must evolve as their enemy has continued to evolve.

McChrystal spoke of his five years in Joint Special Operations Command.

"When I joined this organization - an elite collection of forces -- I thought I was joining an unbeatable team," he said.

In 2004, JSOC was extremely well resourced and highly efficient, McChrystal said. "What we did, we could do better than anyone had ever done it before," he said. "When we went on operations, we had good results, but we were losing the war."

Al Qaeda, on the other hand, focused on being adaptable, McChrystal said.

"Al Qaeda in Iraq became a very resilient, flexible organization, and they were adaptable … and when you pitted adaptable against efficient, surprisingly to us, adaptability won."

As JSOC did, McChrystal stressed that leaders must make adaptability their goal.

But it can't just be about becoming more adaptive killers," Flynn said.

"What I see is there are sufficient numbers of believers in their ideas," he said. "We have to look at the manifestos of why they are doing what they are doing."

One young lieutenant in the audience asked the difference between warfighting and war-winning.

"How do we know that we have won?" he asked Flynn.

Flynn said he wasn't sure how to answer but said: "We have to come to grips with what it is that we are facing. Can we go in and do the kinds of things we know we need to do to take away the will of our enemy?

"It's not about weapon systems. It's not about killing; we are masters at that. This is about removing confidence and removing the will power of an enemy to do what they think they need to do, and I think that is part of the conversation we need to have."

-- Matthew Cox can be reached at Matthew.Cox@monster.com