President Obama, speaking before the United Nations General Assembly, just delivered a speech that reminded me of Hillary Clinton at her most pugnacious, and of John McCain at his most tranquil. He reminded me of the second-term George W. Bush as well.

Obama labeled ISIS "evil" (remember the trouble Bush created for himself when he used such terms?) and promised the destruction of its "network of death"; he excoriated Russia explicitly and at length for bullying its way into Ukraine; he made a direct demand on the Muslim world to disassociate itself from the extreme Islam of ISIS; and, most striking for us here at Goldblog headquarters, he dashed the hopes of the linkage-meisters, the foreign-policy analysts who continue to believe that Israel and its problems represent the core crisis of the Middle East. "Iraq, Syria and Libya should cure ... the illusion that Israeli-Palestinian conflict is the main source of problems in the region,"he said. Five years ago, in his Cairo speech to the Muslim world, Obama labeled the Israeli-Palestinian dispute one of the three major sources of tension between the U.S. and the Muslim world. This bit of analysis has been overcome by events. (He did, though, talk about the unsustainable status quo in the West Bank, something he has talked about before.)

Obama's critics will say that he has shed his public diffidence on matters related to the conflicts of the Middle East because pollsters have been telling him that Americans want a less professorial president. But my impression from watching him in recent weeks, and from talking to people who know him well, is that two sets of recent events in particular have actually shifted his thinking about the relative importance of "soft power"; about the nature of America's adversaries; and consequently about the role the U.S. must play in the world, in order to keep these adversaries at bay.

He understands now that Russia's new czar worships power, and is immune to appeals based on notions of rational self-interest. Obama's forthright promise to stand with America's NATO allies in Eastern Europe, made recently in Estonia, can now be understood as prologue to today's speech.

And he has been truly shaken—as have many people—by the depths of ISIS depravity. And more than that, he realized that no other country apart from the United States had the will or capability to stop ISIS's advance. In other words, Obama understands today that the U.S. is the world's indispensable nation. (Two areas in which Obama was notably discreet: He did not criticize Iran, with which he is trying to negotiate a nuclear deal; and he was distressingly silent on the subject of Bashar al-Assad, who is in many ways the father of ISIS, and is certainly the cause of Syria's collapse. Unlike John McCain, Obama is not interested in confronting Assad at the moment.)

Obama's advisors say that this speech can be placed on a continuum of previous statements. The deputy national security advisor, Benjamin Rhodes, in an e-mail sent after the speech, wrote, "President Obama has always had three themes that appeared prominently today: Calling on nations to meet their responsibilities to uphold international norms; no safe haven for terrorists; (and noting that) ordinary people can bridge divisions of race and religion, and deserve governments who do the same. Remember the August 1, 2007 speech when he said he'd go after Al Qaeda in Pakistan. Or the Nobel address. I think this is in a direct line with those."

Rhodes may be right, but this speech did feel, temperamentally at least, like a break with the past.