In response to a question during the debate in Houston on withdrawing troops from Afghanistan, he said, "The best way not to be caught up in endless wars is to avoid starting one in the first place."
The tail end of that remark prompted the Wall Street Journal to claim that the mayor said the United States started the war in Afghanistan, rather than as a response to the Sept. 11 attacks.
"Let's be very clear, we went to war in Afghanistan, because the United States was attacked," Buttigieg said. "That's why we acted. … What I'm saying is that wars are extremely difficult to end."
Buttigieg, an Afghanistan war veteran, told Stephanopoulos that Sunday marks the five-year anniversary of his leaving the country after serving there in 2014.
"I thought I was one of the very last troops there. We are still there. We are still debating how to get out. So the lesson is, when we're looking at the possibility of new conflicts erupting, like some of the talk around Iran, we better remember how hard it was and is to resolve even a war that we had no choice but to be drawn into."
The mayor was also asked about the recent drone strike on Saudi Arabia's largest oil processing facility. The Trump administration has blamed Iran for the attack, with President Donald Trump calling Saudi Crown Prince Mohammad bin Salman with a message of support.
Buttigieg said that if he were commander-in-chief, his focus would be to make sure "this doesn't escalate into further instability, conflict and not only danger to world oil supply, but danger to peace."
He said the region is already destabilized enough "without fears that a president could destabilize it further with the next tweet."
"We need to make sure right now that we create options to prevent things from escalating further and … making sure that the United States is playing a constructive role in guiding that conflict toward resolution," Buttigieg said. "The good news, in a case like this, when you think about the United States' ability to be a constructive force, is that we have leverage with both sides. We have leverage with the Saudis because of our alliance and have had leverage with Iran. The problem is, we're either taking our own options off the table or not using them well."
During Thursday's Democratic debate on ABC, Buttigieg mostly kept out of the back-and-forth attacks on stage, but jumped in to try to calm tensions when former Housing and Urban Development Secretary Julian Castro inaccurately claimed that former Vice President Joe Biden, 76, didn't remember what he had said about his own health care plan.
"This is why presidential debates are becoming unwatchable," Buttigieg said Thursday night. "This reminds everybody of what they cannot stand about Washington. Scoring points against each other. Poking at each other."
The attack from Castro reignited a discussion on Biden's age and fitness for the presidency. Post-debate, Sen. Cory Booker told CNN, "There's a lot of people who are concerned about Joe Biden's ability to carry the ball all the way across the end line without fumbling."
Asked by Stephanopoulos if he shared the same concern, Buttigieg said that's "for the voters to decide" and no one should be disqualified "as long as you're old enough constitutionally to run."
"Each one of us is competing based on our abilities and based on our vision, and I think that the candidate who has the best abilities and vision is going to prevail. I think we can lay out the differences without hitting below the belt, and that's what I plan to continue to do as a candidate."
One of the main messages for the 37-year-old's campaign is a need for generational change in Washington and he says being from a new generation gives him a different perspective on key issues.
"When we talk about, for example, the fact that by 2050 we have got to be carbon neutral as an economy -- you know, Lord willing, I'm planning to be here to see if we've made it happen. I have a very personal stake in the issues from that to the debt and the deficit, something that's not a fashionable topic among Democrats, but certainly for my generation, that expects to be here when some of these fiscal time bombs go off -- a real concern."
When Buttigieg was on stage during the debate, President Donald Trump took a few jabs at the mayor while at an event in Baltimore.
"They say Buttigieg is two points up in the state of Texas against President Trump. I said, 'I don't think so.' … Think Buttigieg is winning Texas? I've had him up to here," Trump said.
Buttigieg said you can't take the president’s comments seriously and that he's "very curious to know what pollster let him know that I'm beating him in Texas by two points. That's news to me, but it's very good news if it's true."
In the latest national ABC News/Washington Post poll of the Democratic field, Buttigieg drew support from 4% of Democrats and Democratic-leaning independents. Biden topped that list with 27%.
According to that same poll, Buttigieg is shown to be widening his lead since July in a head-to-head matchup against Trump, with a 6-point advantage at 41%-47%.