In his speech today, about terrorism, immigration, and Donald Trump, President Obama looked as ticked off and impassioned as we’ve ever seen him. Photograph by Jim Lo Scalzo-Pool / Getty

This morning, I took a mental-health break from coverage of the attack that took place in Orlando over the weekend. But, at lunchtime, when I turned on NY1 to check the local news, there was President Obama, looking as ticked off and impassioned as we’ve ever seen him. Gone were the lofty detachment and professorial tone that sometimes characterize his oration. In their place were flashing eyes, hand gestures, and a tone that varied from urgency to anger. Speaking for about twenty-five minutes, Obama delivered a ringing defense of his approach to terrorism and a stinging denouncement of Donald Trump and all that he stands for.

Whether Obama intended to deliver such a consequential address, I’m not entirely sure. At times, he appeared to be ad-libbing. But his remarks, which were delivered from a podium in the Treasury Department, where he had met with his national-security staff, turned into perhaps the most important address he has given this year. Indeed, historians may look back on it as one of the defining speeches of his Presidency.

Obama didn’t utter Trump’s name. He didn’t need to. Instead, he began by saluting the Orlando victims and their families. He described the shooter, whom he also didn’t name, as “an angry, disturbed, unstable young man who became radicalized.” By their nature, lone-wolf attacks are hard to stop, Obama pointed out, and he praised the law-enforcement and intelligence efforts that go into preventing them. But, he added, “We are all sobered by the fact that, despite the extraordinary hard work, something like Orlando can occur.”

At this stage, Obama was his usual self: calm and meticulous. Referring to some written notes, he delivered an update on the military campaign against ISIS (ISIL, in the President’s parlance), saying, “This continues to be a difficult fight, but we are making significant progress.” The group, he said, was “under more pressure than ever before,” and had lost more than a hundred and twenty of its military commanders and nearly half of the populated territory that it once held in Iraq. “And it will lose more,” he added.

Turning to the home front, Obama issued another call for “common-sense” gun-control measures, which he rightly insisted were consistent with the Second Amendment. “We have to make it harder for people who want to kill Americans to get their hands on weapons of war that let them kill dozens of innocents,” he said. “People with possible ties to terrorism, who are not allowed on a plane, should not be allowed to buy a gun.” About now, the first glints of irritation, or anger, appeared in the President’s eyes. “Enough talking about being tough on terrorism,” he snapped. “Actually be tough on terrorism and stop making it as easy as possible for terrorists to buy assault weapons.”

With that, Obama paused for a few seconds, as if gathering himself for what he was about to do. “And let me make a final point,” he said. “For a while now, the main contribution of some of my friends on the other side of the aisle in the fight against ISIL has been to criticize this Administration, and me, for not using the phrase ‘radical Islam.’ That’s the key, they tell us. We can’t beat ISIL unless we call them radical Islamists.”

For a moment, Obama looked down. “What exactly would using this label accomplish?” he said, raising his eyes, looking around the room, and gesticulating with his left hand. “What exactly would it change? Would it make ISIL less committed to trying to kill Americans? Would it bring in more allies? Is there a military strategy that is served by this? The answer is none of the above. Calling a threat by a different name does not make it go away. This is a political distraction.”

Obama’s tone had changed: it was harder and more than a little scornful. “Since before I was President, I’ve been clear about how extremist groups have perverted Islam to justify terrorism,” he said. “There’s not been a moment in my seven and a half years as President when we have not been able to pursue a strategy because we didn’t use the label ‘radical Islam.’ Not once has an adviser of mine said, ‘Man, if we really use that phrase, we’re going to turn this whole thing around.’ Not once.”

Trump, of course, is one of the Republicans who has castigated Obama for not using the term “radical Islam.” He did it as recently as Monday. Obama didn’t overtly link his riposte to Trump, but it was clear where he was heading. He said that U.S. Special Forces fighting on the ground in Iraq and Syria know full well who the enemy is, as do the intelligence and law-enforcement officials who spend “countless hours disrupting plots and protecting all Americans, including politicians who tweet”—here, he paused for effect—“and appear on cable-news shows.” There was, he added, “no magic to the phrase ‘radical Islam.’ It’s a political talking point; it’s not a strategy.”

To be sure, it isn’t just Trump and other Republicans who use the term “radical Islam” and its variants. The British Prime Minister, David Cameron, has criticized “Islamist extremism.” The French President, François Hollande, has used the phrase “Islamist terrorism.” (Hillary Clinton also said, on Monday, that she was willing to use the term “radical Islamism.”*) Obama insisted that for him to resort to this sort of language would validate claims by groups like ISIS and Al Qaeda that America is at war with Islam. “That’s their propaganda; that’s how they recruit,” he said. “And if we fall into the trap of painting all Muslims with a broad brush and imply that we are at war with an entire religion, then we are doing the terrorists’ work for them.”

By this point, Obama was gesticulating emphatically with his hands, first one and then the other, for emphasis. “We’re starting to see where this kind of rhetoric and loose talk and sloppiness about who exactly we’re fighting, where this can lead us,” he said. Then he alluded directly to Trump: “We now have proposals from the presumptive Republican nominee for President of the United States to bar all Muslims from emigrating to America. We hear language that singles out immigrants and suggests entire religious communities are complicit in violence. Where does this stop?”

The shooters in the attacks in Orlando and Fort Hood, and one of the killers in San Bernardino, were all U.S. citizens, Obama noted. “Are we going to start treating all Muslim Americans differently? Are we going to start subjecting them to special surveillance? Are we going to start discriminating against them because of their faith? We’ve heard these suggestions during the course of this campaign. Do Republican officials actually agree with this?”

“That’s not the America we want,” he went on. “It doesn’t reflect our democratic ideals. It won’t make us more safe; it will make us less safe, fuelling ISIL’s notion that the West hates Muslims, making young Muslims in this country and around the world feel like, no matter what they do, they’re going to be under suspicion and under attack. It makes Muslim Americans feel like their government is betraying them. It betrays the very values America stands for.” Again, Obama paused. “We’ve gone through moments in our history before when we acted out of fear, and we came to regret it. We’ve seen our government mistreat our fellow-citizens, and it is has been a shameful part of our history.”