In a speech in Youngstown, Ohio, Donald Trump delivered a foreign-policy speech that was long on xenophobia but short on specifics. PHOTOGRAPH BY GERALD HERBERT / AP

A quarter century before he ran for the Presidency, Donald Trump lobbied to be the chief U.S. negotiator with the Soviet Union on a deal to mutually limit their nuclear arsenals. It was in the late eighties, shortly after his book “The Art of the Deal” was on the Times best-seller list for forty-eight weeks. The George H. W. Bush Administration instead tapped Richard Burt, who had spent much of his career in national security. Burt was the Ambassador to West Germany in the run-up to the fall of the Berlin Wall and the collapse of Communism in Eastern Europe. According to a story circulating in Washington, Trump and Burt later met at a society wedding in New York. Trump approached Burt and offered advice on how he would deal with the Soviets. He said that he would initially be the gracious host and ask the Soviet delegation to get comfortable around the table. Then, Trump told Burt, he would stand up, shout “Fuck you!,” and immediately walk out of the room. Burt’s team subsequently concluded the Strategic Arms Reduction Treaty, or START, one of the largest and most complex arms deals in history. (When I asked Burt about the wedding conversation, he would neither confirm nor deny it. The Trump campaign did not respond to a request for comment.)

Yesterday, Trump gave his most detailed speech so far on national security, in Youngstown, Ohio. It, too, relied on simplistic, blunt-force language in outlining his plan to deal with the Islamic State. Sticking closely to the script on a teleprompter, Trump likened the current threat to the Cold War, which lasted almost fifty years, and to Nazism, which killed some six million people in the Holocaust and millions more in the Second World War.

To counter “radical Islamic terrorism,” Trump called for sweeping measures that include the “extreme, extreme vetting” of immigrants, and ideological tests to screen immigrants for “hostile attitudes.” Immigration officers would be empowered to decide who could be expelled. “Those who are guests in our country that are preaching hate will be asked to return home,” he said. Federal investigators and prosecutors across the United States would be tasked with hunting down and prosecuting anyone providing material support—“similar to the effort to take down the Mafia,” Trump said. He also pledged to keep Guantánamo Bay open.

The speech was xenophobic in spirit but vague on specifics. The centerpiece of his plan is the Commission on Radical Islam, which he promised to establish as one of his first acts as President. It would “identify and explain to the American public the core convictions and beliefs of radical Islam, identify the warning signs of radicalization, and expose the networks in our society that support radicalization.” He expressed a willingness to work with “reformist” voices in the Muslim community. He may have few takers. One of the largest Muslims groups in the United States immediately challenged the idea of the Commission as unconstitutional.

“This government promotion of a state version of a particular religion would violate the First Amendment and put America on a path to a society in which those in power get to choose which beliefs are ‘correct’ and which are ‘incorrect,’ ” Robert McCaw, the government-affairs director of the Council on American-Islamic Relations, said. “Trump obviously views millions of ordinary American Muslims not as fellow-citizens who contribute to this great nation but as foreign intruders who must be treated with suspicion and whose constitutional rights may be curtailed.”

In the speech, Trump backed away, a little, from his earlier pledge to ban all Muslim immigrants. Speaking to a largely white audience at Youngstown State University, he said that his Administration would instead deny visas to anyone from a part of the world that breeds terrorism. He didn’t specify which part—and dodged the fact that this now could include many living in Europe. He said that he would ask the Department of Homeland Security and the State Department to draw up a list.

Trump’s strategy to confront the ISIS threat beyond American shores was even vaguer. He spent as much time outlining the litany of attacks by extremist groups as he did detailing policy prescriptions. In a rare departure from his usual speeches, which are ad-libbed, he used wonky language in describing a four-pronged plan in the Middle East. It would, he said, include military operations by a coalition of nations, international coöperation to cut off sources of funding, expanded intelligence sharing, and cyberwarfare to disrupt propaganda and recruiting. This approach scarcely differs from those of the George W. Bush and Obama Administrations in their efforts to combat Al Qaeda and ISIS. The one difference concerns the goal of nation-building, which Trump said he will abandon. As the Bush and Obama Administrations discovered, in both cases reluctantly, nation-building has been pivotal to stabilizing conflict zones.

Trump also called for an international conference of allies to plot strategy abroad. That, too, is hardly new. Over the past fifteen years, the Bush and Obama Administrations have hosted or participated in dozens of conferences to build large coalitions, coördinate operations, or raise donor funds to support Operation Enduring Freedom, in Afghanistan, and Operation Iraqi Freedom.

In a significant flip-flop, Trump said that his Administration would now be willing to work with NATO. Just five months ago, he charged that NATO had become “obsolete”—a word he repeated six times on ABC’s “This Week.” The world’s most powerful military alliance “doesn’t discuss terrorism,” he said in March. “NATO’s not meant for terrorism. NATO doesn’t have the right countries in it for terrorism,” he added. At the time, he suggested the creation of a whole new international coalition as an alternative. In Ohio yesterday, he reversed his position, because NATO had “changed their policy” since his previous comments. The truth is that NATO has engaged in Afghanistan since 2001—its first mission beyond Europe—and has been training Iraqi forces since 2004.

Trump said that he finds “common ground” with Moscow in fighting ISIS. He ignored the fact that President Vladimir Putin, a former K.G.B. officer, has been a primary source of political support—and weapons—for the Syrian President Bashar al-Assad. Assad’s ruthless military repression over the past five years facilitated the rise of radical opposition, including ISIS. Trump also vowed to work with “all others who recognize this ideology of death that must be extinguished.” He excluded Iran from the list of countries he would work with. Although it, too, supports the Assad regime, Shiite Iran has been outspoken about confronting Sunni extremists in ISIS, whose fighters came within twenty-five miles of Iran’s border in 2014. Iran is part of the U.S.-orchestrated bloc of seventeen nations involved in peace talks on Syria. Trump called Iran “the No. 1 state sponsor of radical Islamic terrorism.” On Tuesday, the Russian Defense Ministry announced that its warplanes had started using an Iranian base, near the western city of Hamadan, to bomb Islamic State targets in Syria.

Once again, Trump laid blame for the emergence of ISIS on President Obama and on former Secretary of State Hillary Clinton. Meanwhile, in Scranton, Pennsylvania, a few hours earlier, Vice-President Joe Biden, in his first campaign appearance with Clinton, lambasted Trump’s views on foreign policy as “un-American” and “outrageous.” He warned that Trump’s recent allegation linking Obama to ISIS could endanger American forces deployed against ISIS. The United States has more than four thousand troops currently stationed in Iraq and a few hundred Special Forces helping rebels in Syria. Biden said, “If my son were still in Iraq—and I say to all those who are there—the threat to their life has just gone up a couple clicks.”