WASHINGTON — In a quarrelsome opening debate, Donald Trump continued to accuse Hillary Clinton and President Obama of being responsible for the rise of the Islamic State, while Clinton continued to attack her brash opponent's temperament.

The two presidential contenders clashed aggressively with one another, with each questioning the other's judgment and fitness to serve as commander in chief. Clinton, who has repeatedly attacked Trump as being too thin-skinned to be president, successfully baited Trump into losing his composure, while the former secretary of state stayed poised and made room to showcase her extensive preparation.

Trump, by contrast, seemed to be winging it. When NBC moderator Lester Holt asked the real estate mogul whether he supports the nation's longstanding policy on the first use of nuclear weapons — without explaining the US retains a pre-emptive strike as an option — Trump gave one of his most rambling answers of the night.

Trump first lamented the US' aging arsenal of weapons and equipment in the face of Russia's military modernization and expansion plans — "B-52s old enough that your father or grandfather could be flying them" — and that the US is "not keeping up with other countries," before getting to the topic in a contradictory way.

"I would like everyone to end it, just get rid of it, but I certainly would not do first strike," Trump said. "Once the nuclear alternative happens, it's over. At the same time, you have to be prepared; you can't take anything off the table."

When the heated debate turned to national security in its final third, Clinton used an answer on the importance of US cyber warfare preparedness to attack Trump for his favorable comments about Russian President Vladimir Putin and his invitation to Russia to hack Clinton's email server.  

Trump questioned part of the premise, that Russia hacked the Democratic National Committee — still an unproven allegation.

"I don't think anybody knows it was Russia that broke into the DNC. She's saying Russia, Russia, Russia," Trump said. "I mean, it could be Russia, but it could also be China. It could also be lots of other people. It also could be somebody sitting on their bed that weighs 400 pounds, OK?"

On the Islamic State, Clinton proposed increased airstrikes against the militant group, upping efforts to support Arab and Kurdish partners to "take out" the group, and better targeting of its leaders.

Trump responded by criticizing Clinton for outlining her plan on her website, saying it tips a hand to the enemy. He has said he won't detail his plan because of such concerns.

"She tells you how to fight ISIS on her website. I don't think Gen. Douglas MacArthur would like that too much," he said, using an acronym for the Islamic State group.

With the withdrawal of US forces from Iraq, Clinton and Obama "created a vacuum" that gave rise to the Islamic State, he said.

"No wonder you've been fighting ISIS your entire adult life," Trump said.

"Please, fact checkers, get to work," Clinton retorted.

Clinton referenced an open letter to Trump signed by more than 50 former government officials and national security and military figures, urging him to disclose details of his overseas business investments before Election Day.

But Trump said he he had been endorsed by immigration and customs enforcement agents, and a group of 200 admirals and generals. The full list, he said, would be released next week.

"So when Secretary Clinton talks about this, I mean, I'll take the admirals and I'll take the generals any day over the political hacks that I see that have led our country so brilliantly over the last 10 years with their knowledge, OK," Trump said. "Because look at the mess that we're in."

Later, calling the Middle East a "total mess," Trump assailed Clinton for championing a nuclear deal that he said would allow Iran to develop nuclear weapons, which he called, "another beauty."

On NATO, Trump defended some of his previous comments about members needing to pay their fair share, and the alliance's obsolescence, saying it should "focus on terror also."

Clinton responded NATO has been at war beside the US since the 9/11 attacks, and Clinton defended the Iran deal as derailing the country's imminent plans to form a nuclear bomb and leveling tough multilateral sanctions. She sought to reassure allies that the US would honor its word on mutual defense treaties.

"Words matter," she said.

Trump, at one point said Clinton did not have "the look" or "the stamina" to be president. "To be president of this country, you need tremendous stamina," he said.

Clinton seemed prepared for this.

"Well, as soon as he travels to 112 countries and negotiates a peace deal, a cease-fire, a release of dissidents, an opening of new opportunities in nations around the world or even spends 11 hours testifying in front of a congressional committee, he can talk to me about stamina," Clinton shot back.

Trump declared that he had a stronger temperament.

"I also have a much better temperament than she does, you know?" Trump said. "I think my strongest asset, maybe by far, is my temperament. I have a winning temperament. I know how to win."

Email:  jgould@defensenews.com   

Twitter:  @ReporterJoe

Joe Gould was the senior Pentagon reporter for Defense News, covering the intersection of national security policy, politics and the defense industry. He had previously served as Congress reporter.

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