Gesticulating wildly, Sulaiman Abu Ghaith, Al Qaeda's former spokesman and son-in-law of Osama bin Laden, made a memorable videotaped appearance a month after the September 11 attacks.
He vowed that a "storm of airplanes" would continue to strike American targets.
So it is no surprise that US officials are pleased to finally have him in their custody.
His recent expulsion from Iran reflected what US officials suspect are growing tensions between Tehran and Al Qaeda, particularly over the civil war in Syria, where they back opposing sides.
Abu Ghaith, a Kuwaiti-born teacher and preacher, had spent the past decade under house arrest in Iran, an ideological enemy of Al Qaeda, before being cast out from the country in late January. He was captured in Jordan on February 28 while en route from Turkey to Kuwait, and flown on to New York.
In a Manhattan courtroom this month, Abu Ghaith pleaded not guilty to charges of conspiring to kill US nationals. Prosecutors hailed his arrest as an "important milestone" in counter-terrorism.
Because of his long seclusion in Iran, however, it is unlikely he has operational information about Al Qaeda, analysts said. His significance, instead, could be in the light he may shed on what US officials see as a murky relationship of convenience between Iran and Al Qaeda.
Abu Ghaith, 47, was one of several top Al Qaeda figures and numerous foot soldiers who fled to Iran, along with a sizeable number of bin Laden family members, after the US invaded Afghanistan in October 2001.
Within months, Iran rounded them up. Tehran has long viewed Al Qaeda as a threat, fearing its extremist brand of Sunni radicalism, which is hostile to the Shiite faith of the majority of Iranians.
US officials, however, have often accused Tehran of having a "secret deal" with Al Qaeda, allowing it to funnel funds and fighters through Iranian territory to and from Afghanistan.
Iran's expulsion of Abu Ghaith appears to signal an Iranian crackdown on the terrorist group, US officials said. Two other senior Al Qaeda figures also reportedly left Iran last year, although it was unclear if they were expelled or departed willingly.
Notably, Tehran dispatched Abu Ghaith to Turkey, in effect guaranteeing his capture, rather than to Pakistan, where he could have melted into the shadows.
Even so, US officials maintain Iran is still preserving ties with Al Qaeda by allowing it to use Iranian territory as a transit route.
Tehran denies accusations it ever colluded with Al Qaeda, and many Iran experts doubt there is any significant complicity between them.
Senior Al Qaeda members arrested in Iran after the September 11 attacks "were not active in fighting anybody after that", said a western former diplomat who was in Iran at the time.
"But the Iranians were always scared that Al Qaeda would turn on them," he said. And in March 2003, following the US invasion of Iraq, Tehran reached a "sort of modus vivendi" with Al Qaeda.
As the insurgency in Iraq grew, Al Qaeda operatives could pass through Iran, provided they caused no harm to the Islamic republic en route, he said. That was the "essence of Iran's bad-tempered understanding with Al Qaeda".
Correspondence between senior Al Qaeda operatives found in bin Laden's hideout in Abbottabad, Pakistan, where he was killed by US special forces in May 2011, depicted an adversarial relationship with Iran.
"The Iranians are not to be trusted," bin Laden wrote in an email, while one of his cohorts described Iran as "evil".
There was discussion on ways to threaten Iran, including taking hostages to secure the release of Al Qaeda figures detained in Tehran.
Given this enmity, some argue, Washington had a chance to bring Abu Ghaith to justice a decade ago.
In 2003 Iran offered to return many of its Al Qaeda detainees, including Abu Ghaith, to their home countries, most of which were US allies such as Saudi Arabia, Kuwait and Egypt. Tehran viewed this as a way of easing tensions with Washington, while stopping short of dealing directly with the US, analysts said.
But the US's Arab allies had no appetite to repatriate their wayward Al Qaeda sons, viewing them as too hot to handle. Kuwait refused to take back Abu Ghaith, saying it had stripped him of his citizenship after the September 11 attacks.
"Iran [in 2003] was quite ostentatiously offering to deliver senior Al Qaeda figures to their countries of origin and was turned down. I don't understand why the US didn't encourage this," said Gary Sick, an Iran expert at Columbia University in New York who served on the US National Security Council under presidents Gerald Ford, Jimmy Carter and Ronald Reagan.
Meanwhile, Iran's Al Qaeda captives and the bin Laden family members it was holding remained valuable bargaining chips. By in effect keeping them as hostages, Iran could protect itself from attacks by the terrorist organisation.
In 2010, a teenage daughter of Osama bin Laden "escaped" to the Saudi embassy in Tehran and was allowed to fly to Syria. In return, Tehran secured the release of an Iranian diplomat who was kidnapped 15 months earlier by Sunni militants in Pakistan, who hoped to trade him for bin Laden's kin in Iran.
Some 30 of Osama bin Laden's family members, including several of his children and a dozen grandchildren, spent years in a limbo-like existence in Tehran, cocooned in a walled compound.
Among them, a family member said last week, was Abu Ghaith and his wife, bin Laden's oldest daughter, Fatima, who is now in Saudi Arabia.
In 2010, two of Bin Laden's sons living outside Iran gave sharply differing accounts of conditions at the Tehran compound. One, Khalid, claimed his relatives in Iran were mistreated, "beaten and silenced".
But his half-brother, Omar, insisted they "were very well treated". Life at the compound was comfortable, with a swimming pool and televisions, but constricted.
Occasional telephone calls out were made under Iranian surveillance, mainly to concerned relatives at home. They were mundane, "non-operational communications", a former high-ranking US official told NBC news last week.
None of bin Laden's children or grandchildren remains in Iran, the family member said. Most were released two-and-a-half years ago. "Abu Ghaith was the last out because Iran couldn't find anyone to take him", she said. "They just shooed him away two months ago."
In Iran, Abu Ghaith was safe from the US drone strikes that demolished Al Qaeda's core leadership in Pakistan and Afghanistan in recent years. Now, he faces a maximum penalty of life in prison in the US if found guilty.