I’m not sure President Trump’s speech to the United Nations General Assembly has been fairly judged or received. It was a strong speech — clear, emphatic, remarkably blunt. The great question is whether the bluntness will tend at this point in history to make things better or worse. We’ll find out soon enough.

Often Mr. Trump grows bored with prepared speeches and starts throwing in asides and improvising adjectives. But he was committed to this speech and focused: It looked like Trump believing what Trump was saying. Detractors say, “Oh, his speechwriters just put something in front of him,” but all presidents, from the most naturally eloquent to the verbally dullest, have speechwriters. The point is what a president decides he wants to say and how he agrees to say it. In the end he directs what goes in and what comes out.

Mr. Trump explained to the UN the assumptions he sees as driving his own foreign policy, which showed a proper respect for the opinion of mankind. He outlined the central problems facing the world as he sees them — a tradition in such speeches, and a good one, for it matters what an American president thinks.

Mr. Trump’s speech was rhetorically dense, in that a lot was in it and little time was wasted. There were moments of eloquence — the UN must not be complacent; we cannot become “bystanders to history.”

He began with the usual bragging: The U.S. economy is improving, and we are militarily strong and getting stronger — and fairly quickly kicked into hopefulness, and respect for the UN’s history.

On his administration’s driving foreign-policy attitudes: “We do not expect diverse countries to share the same cultures, traditions or even systems of government. But we do expect all nations to uphold these two core sovereign duties: to respect the interests of their own people and the rights of every sovereign nation.” Then: “In America, we do not seek to impose our way of life on anyone, but rather to let it shine as an example for everyone to watch.”

He painted “America First” as benign, politically realistic. “Our government’s first duty is to its people, to our citizens — to serve their needs, to ensure their safety, to preserve their rights, and to defend their values. As president of the United States, I will always put America first, just like you, as the leaders of your countries, will always and should always put your countries first.” Still, the nations of the world must “work together in close harmony and unity to create a more safe and peaceful future for all people.”

The U.S. has always been “a great friend to the world” and will continue to be. “Our citizens have paid the ultimate price to defend our freedom and the freedom of many nations represented in this great hall,” he said. “We want harmony and friendship, not conflict and strife. We are guided by outcomes, not ideology. We have a policy of principled realism, rooted in shared goals, interests and values.”

All this is the opposite of democracy promotion and nation-building and dreams of eradicating evil. The president has spoken like this before. This section was less statement than restatement for an international audience.

But there was an interesting question of emphasis. Throughout the speech Mr. Trump stressed the importance of national sovereignty, of countries protecting their own ways and needs.

Sovereignty, of course, is crucial. But as he spoke, my mind went back to 1914 and all the fiercely sovereign nations that decided to go to war with each other, putting an end to a unique and rising European civilization. In 1945, after World War II, they put greater emphasis on a more corporate approach, on cooperation and transnational institutions. That path can be abused too, and has been. But it hasn’t been all bad.

It has been charged that Mr. Trump virtually ignored Russia, mentioning it only once, in thanks for supporting sanctions against North Korea. But he also said: “We must reject threats to sovereignty, from the Ukraine to the South China Sea.” That is not ignoring Russia. “We must uphold respect for law, respect for borders, and respect for culture,” he said. “We must work together and confront together those who threaten us with chaos, turmoil, and terror.”

The most publicized section of the speech was on North Korea. He characterized its regime as “depraved,” “twisted,” a “band of criminals.” True enough. North Korea’s “reckless pursuit of nuclear weapons and ballistic missiles” cannot be allowed to continue. In the speech’s most famous flourish: “Rocket Man is on a suicide mission for himself and for his regime.” The U.S. “has great strength and patience, but if it is forced to defend itself or its allies, we will have no choice but to totally destroy North Korea.”

Is this too hot, or helpful, or both? During the Cold War colorful candor produced a great deal. When Ronald Reagan was drop-dead blunt about the nature of the Soviet Union, foreign affairs was a high-stakes chess game between two superpowers. The context now is a less clearly demarcated world in which anyone with a weapon of mass destruction is, for the moment, a “superpower.” It’s hard to know if blunt talk will excite nuts into greater activity, or if bracing clarity about the risks they’re taking will slow them down, make them question their ambitions and intentions.

But the UN needed to hear clearly and unequivocally the gravity with which the American president views North Korea. Ultimately, as Mr. Trump noted, confronting this question is “what the United Nations is for.”

A great line — because it spoke a great truth — was this: “The problem in Venezuela is not that socialism has been poorly implemented, but that socialism has been faithfully implemented.” Mr. Trump then paused and looked at the audience. It struck some as a “please clap” moment. It struck me as a stare-down: I’m saying something a lot of you need to hear. You’re not going to like it, and I’m going to watch you not like it.

Two final points: One is that Mr. Trump is on a roll, a sustained one the past few weeks, and this is new. All levels of government performed well in the hurricanes. Mr. Trump showed competence, focus and warmth. His bipartisan outreach, however it ends, went over well with core supporters and others. He had a strong speech at the UN, in fact a successful UN week, beginning to end. His poll numbers are inching toward 40%.

Which gets us to point two: This is a very important moment for him. History suggests he will ruin it any minute with intemperate statements, wiggy decisions or crazy tweets.

He does this because he’s somewhat compulsive and has trouble governing himself. He also does it because he thinks his supporters like it. Some do, but most don’t. He thinks they all do because he misunderstands his base.

Mr. Trump’s supporters should push back when he starts to go slightly mad. They should tweet at him: “Stop, Donald! Be UN Donald, not Twitter Donald.”

They should tweet this to him by the millions. Because he does feel some loyalty to them, and it’s possible he might try to listen.

Reprinted by permission from peggynoonan.com.