Donald Trump's debate promise that American troops "will do as I tell them" won't include committing war crimes, the Republican presidential frontrunner clarified Friday.

In a statement to the Wall Street Journal, Trump vowed to use "every legal power that I have" to protect America from terrorists. But after a week of concerns that could include targeting civilian family members of suspected terrorists and using torture, the business mogul said he understands there are limits.

"The United States is bound by laws and treaties and I will not order our military or other officials to violate those laws and will seek their advice on such matters," he told the newspaper. "I will not order a military officer to disobey the law. It is clear that as president I will be bound by laws just like all Americans and I will meet those responsibilities."

Just hours earlier, at Thursday's Republican debate, Trump reiterated his plans to "go tougher than waterboarding" on Islamic State group fighters and others threatening national security.

When asked if that includes past promises to have U.S. troops target terrorists' families, Trump said service members would follow his orders.

"I'm a leader. I've always been a leader. I've never had any problem leading people," he said. "If I say do it, they're going to do it. That's what leadership is all about."

Trump's past policy reversals were also a topic at the debate, with moderators and his Republican rivals questioning whether that showed indecision or ignorance of the issues.

He instead called it a strength.

"I've never seen a successful person who wasn't flexible, who didn't have a certain degree of flexibility," he said. "You have to have a certain degree of flexibility. … You have to be flexible, because you learn."

Earlier on Thursday, the last two men to win the Republican nomination for president — Mitt Romney and Sen. Jon McCain, R-Ariz. — both condemned Trump as too reckless and inexperienced to serve as commander in chief.

Leo Shane III covers Congress, Veterans Affairs and the White House for Military Times. He can be reached at lshane@militarytimes.com.