CLEVELAND, Ohio—Former House Speaker Newt Gingrich told a group of Iowa Republicans on Wednesday afternoon that if ISIS terrorists want to live in the eighth century, he has a plan to send them there.

In a preview of his prime-time address to the Republican National Convention on Wednesday night, Gingrich said that "great societies have the capacity to destroy evil people if they have the courage to destroy evil people." He delivered the remarks aboard the Goodtime III, Cleveland's largest excursion ship.

Gingrich said that he "would put assets overhead" to ensure that all modern technology in "any area geographically occupied by ISIS" is targeted by airstrikes.

"I would say that the minute you turn on a car—we're killing you," Gingrich said. "The minute you have an electric generator—we're killing you."

"You're going to have no electricity so you can't be on the internet and you're going to have no cars," Gingrich said. "By the time we're done eliminating your vehicles and by the time we're done eliminating your electricity, if the neighboring folks want to come in and mop you up, that's fine with us."

"We're going to render you literally outside of the modern world," Gingrich said.

Gingrich said ISIS has made clear that it wants "to go back to the eighth century" and that the United States "should facilitate that."

"This is the most powerful nation in the history of the world and we're up against a bunch of guys who are dangerous—they are not a J.V. team—but they haven't got real power—they only have the power we tolerate," he said.

"If we decided to totally degrade their capacity, we could do it in a matter of months, but that would mean the American people would have to decide how ruthless they want to be."

Gingrich said that "in total war, there are no rules."

"I don't know how often you have to see 15 women burned alive, how often you have to see people beheaded, how often you have to see people crucified, to decide these are evil people," Gingrich said. "Great societies have the capacity to destroy evil people if they have the courage to destroy evil people."

Gingrich said earlier in his speech that he has no desire to be named secretary of defense or secretary of state in a hypothetical Donald Trump administration.

"I think [Trump] thought I was going to say I would like to be secretary of state or secretary of defense, but those are real jobs and I'm at a stage in my life where I would really just like to be creative," Gingrich said.

Gingrich told Trump he would rather be named Trump's "chief planner."

"I've told Donald that I would like to be the chief planner," Gingrich said. "What I would really like is a letter that says, ‘Gingrich is in power to review any agency in the federal government and report directly to the president.’"

Gingrich said his convention speech on Wednesday night will focus on national security and foreign policy.