During a national security speech earlier in the day, Trump attacked Clinton for her past support of military action in Iraq and Libya, saying that "she's trigger happy and very unstable, whether we like it or not".
Clinton has spent much of the summer trying to paint Trump as ill-prepared to be commander in chief and too unpredictable to make decisions that put American service members in harm's way.
But both candidates remain unpopular with a majority of the public. He praised the military campaign in Iraq in the first months after the invasion.
He later told an audience in Philadelphia that he would give USA commanders 30 days to come up with a plan to defeat Islamic State, after boasting this week that he has his own "secret plan".
Trump, who followed Clinton at the forum on the USS Intrepid, an aircraft carrier turned museum berthed on the Hudson in NY, was asked about his qualifications for office. Trump's responses, largely a series of word salad jumbles, felt empty.
"For the last 15 years, the work of the Clinton Foundation and the people who rely on it have been President Clinton's life", said Angel Urena, Clinton's spokesman.
Donald Trump told NBC's Matt Lauer he "was totally against the war in Iraq".
Bob Corker, the Republican chairman of the Senate Foreign Relations Committee, repeatedly refused to say directly whether he had confidence in Trump as commander in chief when questioned on MSNBC's "Morning Joe" on Wednesday.
MADDOW: But to have half of the time with her be on the issue e-mail?
Trump's rival, Democrat Hillary Clinton, has tried to paint the billionaire businessman as erratic, making the case that his disposition would be a major liability on the world stage. At yet, at other times she was vague, like when she promised to defeat ISIS without explaining how.
"We have to defeat ISIS".
For example, the size of the U.S. Army swelled to about 570,000 at the peak of the Iraq war, building up to meet deployment demands. He said when we go out-and he took everybody out. When Lauer said Russian Federation is suspected of hacking USA political system, Trump said, "Nobody knows that for a fact" and said of Putin, "If he says great things about me, I'm going to say great things about him". "If (Putin) says great things about me, I'm gonna say great things about him. If we would have taken the oil, you wouldn't have ISIS". "Far more than our president has been a leader". In one instance, he said the United States should pull back thoroughly from Iraq, and then said troops should be left behind in "various sections where they have the oil", to secure USA energy interests. But there now are almost 6,000 US troops in Iraq, some less than 50 miles from the ISIS-controlled city of Mosul, its capital in Iraq.
Trump, though, was the king of falsehoods during the forum: he suggested there was no military judiciary system in place to prosecute those accused of crimes like rape.
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A woman in the audience asked Trump during the forum what he'll do to stop the "20 veterans" from committing suicide daily.
And he said ISIS was allowed to rise because it stole oil that the US should have taken as its war bounty in Iraq. He caused a stir by defending a tweet that implied military sexual assault is a result of women serving in the military. He also opened the door to granting legal status to illegal aliens if they join the military.
The Democratic presidential nominee "is the only candidate that has the experience, temperament, critical thinking and level-headed leadership to keep America safe and our partnerships strong", said Air Force Gen. Lloyd Newton. But her past reluctance to take questions from a freewheeling pack of traveling journalists - commonplace in presidential politics - has fueled criticism about her relatability and provided ammunition to Republicans and their nominee, Donald Trump, who have accused her of hiding to avoid scrutiny. I think the Iraqi situation is a problem.
Trump's donation came days after Bondi's office said it was weighing an investigation into allegations of fraud against the scandal-ridden Trump University. "They've gotta now get into Mosul". Commanders are expected to give their best objective military advice and to not to be persuaded by the political ramifications of such recommendations.