For three years, as undersecretary of state for public diplomacy and public affairs, I would not and could not utter that phrase.
No one in the Obama administration could or did. We used the much less specific term "violent extremism". As in "countering violent extremism", which is what we called much of our anti-Islamic State in Iraq and Syria (ISIS) efforts.
And for all of that time, we were collectively excoriated by conservatives, Republicans and Mr Donald Trump.
"These are radical Islamic terrorists, and she won't even mention the word, and nor will President Obama," Mr Trump said, referring to Mrs Hillary Clinton at a presidential debate last year. "Now, to solve a problem, you have to be able to state what the problem is, or at least say the name."
The implication is that we were all somehow too timid or too politically correct to say it.
But the reason was a much more practical one: To defeat radical Islamic extremism, we needed our Islamic allies - the Jordanians, the Emiratis, the Egyptians, the Saudis - and they believed that term unfairly vilified a whole religion.
They also told us that they did not consider ISIS to be Islamic, and its grotesque violence against Muslims proved it. We took a lot of care to describe ISIS as a terrorist group that acted in the name of Islam.
Sure, behind the scenes, our allies understood better than anyone that ISIS was a radical perversion of Islam, that it held a dark appeal to a minority of Sunni Muslims, but it didn't help to call them radical Islamic terrorists.
Now the Trump administration wants to toss out the term "violent extremism" and the rubric we used to fight it.
Instead, they are renaming it "countering Islamic extremism", or "countering radical Islamic extremism". Fine. Abandon the name but let's not abandon the strategy.
First, let's acknowledge that it's working. ISIS as a military force, much less as a caliphate, is on the ropes in Iraq and Syria.
The group has not had a military victory in a year and a half. The flow of foreign fighters into Iraq and Syria is down by 90 per cent, according to the Defence Department. The liberation of Mosul is on the horizon.
ISIS will go away, but violent extremism will not.
The way to defeat radical Islamic extremism is to help our Islamic allies and promote the voices of mainstream Islam that reject everything ISIS does and stands for. Defeating ISIS on the military battlefield is only temporary. Violent extremism - or whatever you call it - must be defeated on the battlefield of ideas.
Second, let's recognise the truth of what King Abdullah of Jordan has said over and over: "This is our fight."
And by that, he meant that it is Islam's fight.
It is a misconception that ISIS is focused on fighting us. I led the State Department's agency that sought to counter ISIS's propaganda efforts and saw this first-hand. More than 80 per cent of its propaganda is in Arabic. Russian is the second most-used language, while English and French are tied for third. The United States is not ISIS's main audience. We have always been the distant enemy.
So, jettison "violent extremism", but let our Arab allies know that "radical Islam" or "Islamic extremism" refers only to the tiny fraction of the world's 1.6 billion Muslims who have embraced violence. Tell them we need their help both on the military battlefield, and in the information and intelligence space. And be specific: "We are fighting ISIS and Al-Qaeda, and their radical Islamic imitators like Boko Haram."
After all, "radical Islam" is only a shade less vague than "violent extremism". ISIS is not just a terrorist group, it is an idea. Its rallying cry is that the West is hostile to Islam and that every good Muslim has a duty to join the caliphate. Most of the group's propaganda was not violent at all. I saw thousands of tweets about how beautiful the caliphate was. There were videos of kids on Ferris wheels and fighters distributing cotton candy. I remember one tweet showing a shiny apple and the words, in Arabic, "The caliphate is bountiful."
It is not up to us to say what is Islamic and what is not. Only the voices of mainstream Muslims and independent clerics in Muslim countries can create a narrative that refutes ISIS's and offers a more positive alternative.
A tweet from the US government saying ISIS is a distortion of Islam is not going to hurt the group. Instead, it will help its recruiting.
That is why the Trump administration's executive order on immigration from seven Muslim-majority nations is deeply counterproductive in the fight against Islamic extremism.
It has already been reported that ISIS has called it "the blessed ban" because it supports its position that the US hates Islam.
The clause in the order that gives Christians preferential treatment will be seen as confirming ISIS's apocalyptic narrative that Islam is in a fight to the death against the Christian crusaders.
The images of Muslim visitors being turned away at US airports will only inflame those who seek to do us harm.
Two years ago, just before Ramadan, ISIS spokesman Abu Muhammad Al-Adnani said: "Don't bother coming to the caliphate, but commit acts of violence against the enemy wherever you are."
The call was no longer religious or ideological - what the group sought to do was exploit vulnerability. Adnani was, in effect, saying, "Whatever angers you - whether it's your boss or your neighbours or the police - commit acts of violence in ISIS's name."
Thus, the black flag of ISIS became a flag of convenience for any complaint. Now the travel ban, despite being blocked by the courts, has given the group ammunition to weaponise grievance here in the US. President Trump may become its No. 1 recruiting tool.
ISIS will go away, but violent extremism will not.
The way to defeat radical Islamic extremism is to help our Islamic allies and promote the voices of mainstream Islam that reject everything ISIS does and stands for.
Defeating ISIS on the military battlefield is only temporary. Violent extremism - or whatever you call it - must be defeated on the battlefield of ideas.
Richard Stengel is a fellow at Harvard's Kennedy School.
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