This unilateral approach makes for good television, but this is the real world, in which other nations have agendas, too. Mr. Trump says he is “going to be working very closely with our allies in the Muslim world, all of which are at risk from radical Islamic violence.” But how will he gain cooperation for his “unpredictable” war on the Islamic State while enforcing a “pause” that prevents Muslims from entering this country, and forcing those living here to register themselves?

How does one “apply leverage on China necessary to rein in North Korea,” while slapping a trade-killing tariff on Chinese imports? It’s correct that many of our NATO allies aren’t paying their agreed-upon share of its costs — but what happens to the United States’ overseas bases if we “walk?”

While trumpeting America’s role in winning World War II and the Cold War, Mr. Trump simultaneously pronounced that “America First,” the 1930s isolationist theme that he quoted without attribution, “will be the major and overriding theme of my administration.” He did not bother to square that with his vow not to “hesitate to deploy military force when there is no alternative.” He condemned “nation building,” but said he aims to build “regional stability,” without explaining the difference.

Mr. Trump decried a shrinking American military and the deterioration of the nuclear arsenal. But he did not say how he would further build up the military — which has a budget this year of nearly $600 billion — while cutting government spending, which he also wants to do. And he seems to be ignorant of the sweeping $1 trillion effort to revitalize the nuclear force that is already underway.

Mr. Trump repeatedly states outright falsehoods, often based on wrong assumptions. He’s been refuted before on his claim that the Islamic State is making “millions of dollars a week” by selling Libyan oil. There is zero evidence of that. The nuclear deal with the United States and other major powers has not made Iran a “great power,” nor has Tehran violated the conditions of that pact, as Mr. Trump has said.