President Donald Trump delivered a speech to his alt-right, antiglobalist base from the podium of the United Nations General Assembly on Tuesday. He offered a vision of America’s role in the world starkly different from any of his predecessors who stood in the same spot before the leaders of the world — remarks antithetical to the ideals that led the United States to play a central role in the U.N.’s founding in the wake of World War II.

Trump spoke frequently about “sovereignty,” so frequently it became the central theme of his speech. “[W]e do expect all nations to uphold these two core sovereign duties: to respect the interests of their own people and the rights of every other sovereign nation,” he said. National sovereignty, of course, has been the foundational tenet of international affairs for centuries. But Trump’s words were code. They spoke to the fears of the Breitbart crowd that U.S. collaboration with other nations in a global organization means giving up its sovereignty.

Trump also lashed out at “global bureaucracies” and international trade accords. He complained that the United States was spending too much on the U.N. This attack on the U.N. comes in conjunction with his withdrawal from the Paris climate accord and the Trans-Pacific Partnership; his goal of renegotiating the North American Free Trade Agreement; his threats to undo the U.S.-South Korea trade deal and the Iran nuclear deal; as well as his criticism of our NATO allies.

Overall, Trump’s speech reinforces his position as the most nationalist U.S. president of modern history.

Trump offered an ideology that he called “realistic” but that at its heart was selfish. All foreign policy is guided by national interests. But while Trump praised some U.N. programs, time and time again his approval seemed clearly grounded in a philosophy of “what’s in it for us” that seemed to set aside the values of community and common interests on which the U.N. was founded. This was perhaps best illustrated by the case he made against what he called “uncontrolled migration” and his arguments that the best place for refugees is, in his view, as far from the United States as possible.

Beyond pragmatism, the speech likely will be remembered as one in which the president of the United States sounded more like a mob boss than a statesman. This was a tough guy flexing his muscles so that all in the audience could see how tough he was.

His harshest language was reserved for North Korea. Outlining the threat it poses, he then went on to say that if it did not “denuclearize,” “we will have no choice but to totally destroy North Korea. Rocket Man is on a suicide mission.”

These are words never to be engraved in marble. The president of the United States chose, in a forum dedicated to diplomacy, to threaten to wipe another nation — a much smaller one — off the face of the Earth in language that was not so much hard-line rhetoric as it was schoolboy bullying complete with childish name-calling.

Trump also used language so harsh about the Iran nuclear deal that it seems highly unlikely that he will be able to avoid pulling out of it without appearing to be a complete hypocrite. (And attacking as vehemently as he did the most prominent recent effort to denuclearize a country by diplomatic means rather than via force, even if that effort was flawed, seems to make a peaceful solution to the North Korean crisis less rather than more likely.)

In the wake of Trump’s remarks, I was told by sources at the U.N. that many diplomats were shaken by the starkness of his words.

But why, if Trump was going to take such a strong stance for sovereignty, did he neglect to mention the most aggressive attack on U.S. sovereignty — specifically, our ability to conduct free and fair elections — that has taken place in recent years or the attacker, Russia? On this, the big tough guy was strangely silent. Well, not so strangely.

In short, Trump gave a speech that may have shocked the world but that could not have surprised a single American who has watched his narcissistic cave-man routine for the past two years. His words could carry with them a globally destabilizing effect. At home, the speech no doubt will get cheers from the president’s xenophobic base and result in deepening dismay from all the rest of us.