FORT DODGE, Iowa — As Donald Trump took the stage in a community college theater on Thursday night, something was off.

The usually punctual executive was nearly 40 minutes late. His voice was hoarse, his hair mussed, his tone defensive. He promised to take questions from the audience but instead launched into a 95-minute-long rant that at times sounded like the monologue of a man grappling with why he is running for president — and if it's really worth it or not. Even for a candidate full of surprises, the speech was surprising.

He scoffed at those who have accused him of not understanding foreign policy, saying he knows more about Islamic State terrorists "than the generals do." He took credit for predicting the threat of Osama bin Laden and being right on the "anchor baby situation," a position he says "these great geniuses from Harvard Law School" now back. He uttered the word "crap" at least three times, and promised to "bomb the s---" out of oil fields benefiting terrorists. He signed a book for a guy in the audience and then tossed it back at him with a flip: "Here you go, baby. I love you."

Trump called Republican rival Carly Fiorina "Carly whatever-the-hell-her-name-is," accused Democratic front-runner Hillary Rodham Clinton of playing the "woman's card" and said Sen. Marco Rubio (R-Fla.) is "weak like a baby." He then devoted more than 10 minutes angrily attacking his chief rival, Ben Carson, saying the retired doctor has a "pathological disease" with no cure, similar to being a child molester.

"If I did the stuff he said he did, I wouldn't be here right now. It would have been over. It would have been over. It would have been totally over," Trump said. "And that's who's in second place. And I don't get it."

[GOP elites in a near panic that Trump or Carson could win]

For months, Trump has defied the traditional rules of politics, saying and doing things that would end the presidential ambitions of most candidates — and often to the chagrin of Republican leaders who can't believe that a billionaire reality television star has built such a dedicated following and dominated the polls for so many months. As some waited for an implosion of Trump's improbable campaign, the Republican front-runner began to show much more composure and control on the campaign trail. During the latest debate, he largely refrained from attacking those on stage with him, instead focusing on the policy questions asked.

[As challengers approach, a different Donald Trump emerges]

But Trump appeared to unravel on stage Thursday evening before a crowd of roughly 1,500 in Fort Dodge, a small industrial town 100 miles northwest of Des Moines. Many in the crowd were community college students who have never voted in a presidential election, along with teachers, local politicians and a number of farmers from the area. Rather than sticking to his usual, tidy 60 minutes, Trump kept going and going. Campaign staffers with microphones had planned to solicit questions from the audience, but instead stood waiting in the aisles, then sat for a while, then stood again at attention. Those standing on risers behind Trump — providing a backdrop of Iowan faces — eventually gave up and sat down in a falling cascade.

At first, the audience was quick to laugh at Trump's sharp insults and applaud his calls for better care for veterans, to replace the Affordable Care Act, and to construct a wall along the Mexican border. But as the speech dragged on, the applause came less often and grew softer. As Trump attacked Carson using deeply personal language, the audience grew quiet, a few shaking their heads. A man sitting in the back of the auditorium loudly gasped.

The tirade came amid one of Trump's busiest weeks yet on the campaign trail. Trump hosted "Saturday Night Live" last weekend and then spent Sunday doing interviews. Monday night he had a rally in Illinois. Tuesday night was the fourth GOP debate in Milwaukee. Wednesday morning, after about 90 minutes of sleep, Trump attended a breakfast in New Hampshire. Thursday he arrived in Iowa for a tour of a factory, television interviews and the rally at the community college.

Trump's tear started hours before the rally. On Twitter, he slammed Carson, "dopey Karl Rove" and the Wall Street Journal editorial board. In a CNN interview, Trump accused Rubio of supporting amnesty for illegal immigrants already in the country simply because he's Hispanic. A few of Trump's fans learned about the rally speech on Twitter and accused reporters of fabricating the quotes and tweeting them out in unison. Video later posted online showed that Trump indeed had said these things.

Trump opened the rally with a defense of his often-criticized proposal for dramatic immigration reform. He explained how other countries punish illegal border crossers: North Korea requires 12 years of hard labor, he said, while Afghanistan shoots people, and Canada assesses a fine of $5,000.

"If you cross the United States border illegally, you get a job, you get a drivers license … you get food stamps, you get a place to live, you get health care, housing, child benefits and in many cases education," Trump said. "You wonder why we're a debtor nation. You wonder why our country is going to hell."

Throughout the evening, Trump kept coming back to this point: The country is going to hell, and something must be done. And it was a message that the audience seemed to savor.

"We're in this thing together, folks. We've got to get out of it," Trump said at one point. And later: "We're just not going to take it any more."

Trump described traditional politicians as "stupid" and told the crowd that he is "competent." That's why he got so angry when journalists forced him to share his strategy for fighting the Islamic State, even though he wanted to keep such plans secret so as not to tip off the enemy, he said. Journalists, he said, are "scum" and "garbage."

"I know more about ISIS than the generals do," Trump said. "Believe me."

Trump said he would go after the oil fields in Iraq and Syria that he says nets the terrorist group "millions of dollars a week."

At a rally in Iowa, Republican presidential candidate Donald Trump said he would take an aggressive stance against the Islamic State, vowing to "bomb the s---" out of their oil-rich territories. (Reuters)

"I would bomb the s--- out of them," he said to raucous applause. "I would just bomb those suckers. And that's right: I'd blow up the pipes, I'd blow up the refineries. I would blow up every single inch. There would be nothing left."

The applause was nowhere near as strong as Trump launched into a lengthy critique of Carson, who is well-liked in Iowa and has at times beat Trump in polls here. The Iowa caucuses are often dominated by evangelicals, many of whom have been captivated by Carson, who talks endlessly about his faith.

[Trump's attacks on Carson turn personal]

Carson wrote in his autobiography that as a young man he had a "pathological temper" that caused him to violently attack others — going after his mother with a hammer and trying to stab a friend, only to have the blade stopped and broken by the friend's belt buckle. In recent days, those accounts have come under scrutiny, and Carson has had to clarify or correct some of the details.

Trump said Carson has a "pathological disease" with no cure, comparing it to the incurable mental conditions of child molesters.

"A child molester, there's no cure for that," Trump said. "If you're a child molester, there's no cure. They can't stop you. Pathological? There's no cure."

With his voice growing louder and louder, Trump questioned what sort of person would attack his mother. He questioned how a belt buckle could stop a blade, stepping away from the podium to demonstrate how such an attack might happen and how his own belt buckle wouldn't stay in place long enough to stop a knife.

"Anybody have a knife?" Trump asked the audience, which was screened by Secret Service agents who began protecting him this week. "You want to try it on me?"

Trump was flabbergasted: "How stupid are the people of Iowa? How stupid are the people of the country to believe this crap?"

And Trump said he doesn't believe that after just a few hours of reflection, Carson found God and overcame his violent temper.

"He goes into the bathroom for a couple of hours, and he comes out, and now he's religious," Trump said. "And the people of Iowa believe him. Give me a break. Give me a break. It doesn't happen that way. It doesn't happen that way. … Don't be fools, okay?"

Trump told the audience that while he might not be "a perfect Christian" like Carson, he has leadership abilities that Carson does not have.

"I know how to do it," Trump said of the presidency. "I really know how to do it."

After 95 minutes, Trump drew to a sudden but long-awaited end. Gripping the podium, he promised to unify the country and win. He also wondered aloud if he should just move to Iowa and buy a farm.

"I've really enjoyed being with you," Trump said. "It's sad in many ways because we're talking about so many negative topics, but in certain ways it's beautiful. It's beautiful."