How does the US plan to ‘degrade and destroy’ the Islamic State?

It’s unclear when freelance journalist Steven Sotloff was killed. The video showing his execution video was posted online Tuesday, two weeks after Islamic State insurgents showed the world another beheading of an American journalist, James Foley. Both reporters were kidnapped in Syria amid its civil war.

While visiting Tallinn, Estonia, President Barack Obama took a moment to address the killings.

"Whatever these murderers think they will achieve by killing innocent Americans like Steven, they have already failed. They failed because, like people round the world, Americans are repulsed by their barbarism," he said.

Last week Obama said he had not yet developed a strategy for confronting the Islamic State in Syria and Iraq. By this week the chorus of criticism from Capitol Hill grew louder.

"We can't wait forever, and the longer we do wait, the stronger ISIS becomes," said Rep. Peter King, R-N.Y., using an acronym for another name for the group.

"He's very cautious. Maybe in this instance too cautious," said Sen. Dianne Feinstein, D-Calif.

"The president of the United States is either in denial or overwhelmed," said Sen. John McCain, R-Ariz.

Last month Obama authorized airstrikes against the Islamic State in Iraq, and he said the limited military campaign has been fruitful.

In Estonia he said, "Our objective is clear, and that is to degrade and destroy ISIL [another abbreviation for the group] so it’s no longer a threat, not just to Iraq but also to the region and to the United States." 

How he plans to do that remains unknown, but he vowed, "Those who make the mistake of harming Americans will learn that we will not forget and that our reach is long and that justice will be served."

Why does the Islamic State appear to be provoking U.S. military action in the region?

Can Obama take action in Iraq but not in Syria?

How will he "degrade and destroy" the Islamic State?

We asked a panel of experts these questions on this edition of "Inside Story."