No presidential candidate in modern times has ordered American priorities that way, and even here, several speakers have called for a far more interventionist policy, more reminiscent of George W. Bush’s party than of Mr. Trump’s.  But Mr. Trump gave no ground, whether the subject was countering North Korea’s missile and nuclear threats or dealing with China in the South China Sea. The forward deployment of American troops abroad, he said, while preferable, was not necessary.  “If we decide we have to defend the United States, we can always deploy” from American soil, Mr. Trump said, “and it will be a lot less expensive.”  Many military experts dispute that view, saying the best place to keep missile defenses against North Korea is in Japan and the Korean Peninsula. Maintaining such bases only in the United States can be more expensive because of the financial support provided by Asian nations.  Mr. Trump’s discussion of the crisis in Turkey was telling, because it unfolded at a moment in which he could plainly imagine himself in the White House, handling an uprising that could threaten a crucial ally in the Middle East. The United States has a major air base at Incirlik in Turkey, where it carries out attacks on the Islamic State and keeps a force of drones and about 50 nuclear weapons.  Mr. Trump had nothing but praise for President Recep Tayyip Erdogan, the country’s increasingly authoritarian but democratically elected leader. “I give great credit to him for being able to turn that around,” Mr. Trump said of the coup attempt on Friday night. “Some people say that it was staged, you know that,” he said. “I don’t think so.”  Asked if Mr. Erdogan was exploiting the coup attempt to purge his political enemies, Mr. Trump did not call for the Turkish leader to observe the rule of law, or Western standards of justice. “When the world sees how bad the United States is and we start talking about civil liberties, I don’t think we are a very good messenger,” he said.  The Obama administration has refrained from any concrete measures to pressure Turkey, fearing for the stability of a crucial ally in a volatile region. But Secretary of State John F. Kerry has issued several statements urging Mr. Erdogan to follow the rule of law.  Mr. Trump offered no such caution for restraint to Turkey and nations like it. However, his argument about America’s moral authority is not a new one: Russia, China, North Korea and other autocratic nations frequently cite violence and disorder on American streets to justify their own practices, and to make the case that the United States has no standing to criticize them.  Mr. Trump said he was convinced that he could persuade Mr. Erdogan to put more effort into fighting the Islamic State. But the Obama administration has run up, daily, against the reality that the Kurds — among the most effective forces the United States is supporting against the Islamic State — are being attacked by Turkey, which fears they will create a breakaway nation.  On the third day of the Republican convention, the refusal by Senator Ted Cruz to endorse Donald J. Trump widened cracks in the party’s veneer.  Asked how he would solve that problem, Mr. Trump paused, then said: “Meetings.”  Ousting President Bashar al-Assad of Syria, he said, was a far lower priority than fighting the Islamic State — a conclusion the White House has also reached, but has not voiced publicly.  “Assad is a bad man,” Mr. Trump said. “He has done horrible things.” But the Islamic State, he said, poses a far greater threat to the United States.  He said he had consulted two former Republican secretaries of state, James A. Baker III and Henry Kissinger, saying he had gained “a lot of knowledge,” but did not describe any new ideas about national security that they had encouraged him to explore.  Mr. Trump emphatically underscored his willingness to drop out of Nafta unless Mexico and Canada agreed to negotiate new terms that would discourage American companies from moving manufacturing out of the United States. “I would pull out of Nafta in a split second,” he said.  He talked of funding a major military buildup, starting with a modernization of America’s nuclear arsenal. “We have a lot of obsolete weapons,” he said. “We have nuclear that we don’t even know if it works.”  The Obama administration has a major modernization program underway, focused on making the nuclear arsenal more reliable, though it has begun to confront the huge cost of upgrading bombers and submarines. That staggering bill, estimated at $500 billion or more, will land on the desk of the next president.  Mr. Trump used the “America First” slogan in an earlier interview with The New York Times, but on Wednesday he insisted he did not mean it in the way that Charles A. Lindbergh and other isolationists used it before World War II.  “To me, ‘America First’ is a brand-new, modern term,” he said. “I never related it to the past.”  He paused a moment when asked what it meant to him.  “We are going to take care of this country first,” he said, “before we worry about everyone else in the world.”
Reiterating a hard-line nationalist approach, Mr. Trump raised new questions about his commitment to automatically defend NATO allies.