What to do if US begins capturing more suspected terrorists?

Throughout Obama's presidency, suspects have been killed in drone strikes or raids, or captured and interrogated, sometimes aboard Navy ships.

Rebecca Ingber, an associate law professor at Boston University who follows the issue, warns that if the U.S. engaged in a full ground war in Syria, "chances are there would need to be detention facilities of some kind in the vicinity."

Obama has not sent a single suspected terrorist to the U.S. military prison at Guantanamo Bay, Cuba, where many have been detained for years without being charged or tried — something the president says is a "recruitment tool" for militant extremists.

Sen. Kelly Ayotte, R-N.H., believes that the absence of a long-term detention and interrogation facility for foreign terrorist suspects represents a "major shortcoming in U.S. national security policy."

Since it was established in 2009, that team has been deployed 34 times, Thompson said, adding that other government agencies conduct independent interrogations as well.

Brett McGurk, special presidential envoy for the global coalition to counter IS, told Congress this month that in the final six months of 2015, 90 senior to midlevel leaders were killed, including the IS leader's key deputies:

Ali Soufan, a former FBI agent who investigated and supervised international terrorism cases, including the U.S. Embassy bombings in East Africa and the attack on the USS Cole in Yemen the 1990s, said sending suspected terrorists through the American criminal justice system works.

"The current practice of investigating and prosecuting terror suspects has proved incredibly effective," Soufan said, noting that since the Sept. 11 attacks in 2001, only seven people have been tried and convicted under military commissions.