Republican presidential candidates have competed to take the toughest stance on fighting Islamic State, and Sen. Ted Cruz has some ideas about the aggressive tactics he'd like to use.

On the campaign trail, Cruz has said he wants to "carpet bomb" the Islamic militants and find out whether "sand can glow in the dark." Asked about the idea during Tuesday night's debate in Las Vegas, the Texas senator said the United States should use "overwhelming air power" against the militant group.

Carpet bombing means saturating an area with explosives.

Wolf Blitzer, the CNN anchor moderating the debate, pushed Cruz for more details.

"Would you carpet bomb Raqqah, the ISIS capital, where there are a lot of civilians? Yes or no?" Blitzer asked, using another name for Islamic State.

Cruz said no.

"You would carpet bomb where ISIS is, not a city, but the location of the troops," Cruz said. "You use air power directed -- and you have embedded special forces to direction the air power. But the object isn't to level a city. The object is to kill the ISIS terrorists."

That answer didn't impress some watching the debate.

Note to Cruz: ISIS embeds itself in cities. If you carpet bomb them, you destroy cities. Also, it won't stop them. #GOPDebate — Josh Rogin (@joshrogin) December 16, 2015

You can't carpet bomb an insurgency out of existence. This is just silly, but it sounds stalwart — Rich Lowry (@RichLowry) December 16, 2015

There were also concerns about the tactic of carpet bombing. The term suggests indiscriminate destruction, something that could violate the Geneva Conventions.

Carpet bombing & intentionally targeting children & other non-combatants are war crimes. Suggesting this as US strategy is outrageous. — AmnestyInternational (@amnesty) December 16, 2015

Democratic presidential candidate Hillary Clinton has also mocked Cruz's insistence on carpet bombing, most recently in a Tuesday speech before the Republican debate.

"Promising to carpet bomb til the desert glows...makes you sound like you are in over your head" @HillaryClinton says of @tedcruz strategy — Evan Halper (@evanhalper) December 15, 2015

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