Donald Trump says people in the United States illegally are cared for better than the nation's military veterans.
Mr Trump was speaking at the annual Rolling Thunder motorcycle rally, which honours prisoners of war and service members missing in action.
Mr Trump was warmly received by the crowd despite having once said he prefers "people who weren't captured" when criticising Arizona Senator John McCain, a war prisoner during Vietnam.
Mr Trump told the crowd that if elected he plans to "knock the hell out of" the Islamic group by building a bigger, better military.
He also reiterated his promise to build a wall to keep out people from entering the country illegally.
"Who's going to pay for the wall?" he bellowed. The crowd yelled back: "Mexico."
''Not even a doubt," he replied.
The US congress and many states have written an assortment of laws and policies designed to restrict government services to people in the country illegally.
Veterans groups were furious following Mr Trump's comments about Mr McCain but, despite not apologising to the former Republican presidential nominee, he has worked to try to repair the damage.
He frequently honours veterans at his rallies and has come out with a plan to overhaul the Department of Veterans Affairs.
He also held a fundraiser for veterans' causes in place of an Iowa debate that he missed.
But Mr Trump, who avoided military draft through a series of deferments, attracted scrutiny for not immediately distributing the 6 million US dollars he had claimed to raise, including 1 million dollars he had pledged himself.
He is expected to hold a news conference on Tuesday to announce the name of the charities selected to receive the money.
Mr Trump said he would cut waiting times for veterans needing medical care.
"If there's a wait, we're going to give the right for those people to go to a private doctor or even a public doctor and get themselves taken care of and we're going to pay the bill," he said.
Mr Trump has a loyal following with bikers, who frequently attend his rallies, where they sometimes clash with Trump protesters.
Among those eager to hear Mr Trump speak was Louis Naymik, 52, of Clarksburg, Maryland, who said he served in the Ohio Army National Guard for four years.
"There's history in the air here," he said. "We're living in historic times in our country today with the election and the choosing of a new president. And I just wanted to give honour to those who have fallen and sacrificed their lives for our country."
Mr Naymik, who works in radiology, was wearing a Trump shirt and said he had been a supporter since the day Trump announced his candidacy
"What I like about Trump is that he is one of us. He's not a politician," he said, adding that Mr Trump would bring the country back to its old values, put American citizens first and honour its veterans.