Did you know that the alleged ringleader in the 11 September 2001 attacks had originally planned to land one of the hijacked US airliners and give a speech to the assembled press corps? Can you guess what he wanted to rant about, live on Fox News? Seventy-two virgins in heaven? Nope. The need for sharia law? Guess again. According to the report of the official 9/11 commission, Khalid Sheikh Mohammed had intended to "deliver a speech excoriating US support for Israel... and repressive governments in the Arab world".
In the vexed discussion about extremism and radicalisation, foreign policy is the issue that dare not speak its name. Our leaders zealously police the parameters of the debate, pre-emptively warning off those who might dare connect the dots between wars abroad and terror at home. It would be "wrong", said the Mayor of London, Boris Johnson, on the morning after the attack in Woolwich, "to try to draw any link between this murder and British foreign policy".
Really? The problem for Johnson is that the "link" was made by none other than one of the suspects in the barbaric killing of Drummer Lee Rigby, Michael Adebolajo. Straight after the murder. On camera. "The only reason we killed this man... is because Muslims are dying daily," he said. "This British soldier is an eye for an eye, a tooth for a tooth." Are we expected to ignore such statements? Or notice only the references to "Muslims"?
To highlight this is to invite inevitable and hysterical criticism; I will be accused of apologising for acts of terror, or condoning them. So permit me to issue a pre-buttal: there is no moral justification for the deliberate killing of non-combatants. Nothing - no cause, no war, no grievance - justifies the murder of innocents. Yet establishment figures continue to denounce those of us who cite the radicalising role of foreign policy as (to quote the former US state department spokesman James Rubin) "excuse-makers" for al-Qaeda. To explain is not to excuse. The inconvenient truth for Rubin, Johnson et al is that Muslim extremists usually cite political, not theological, justifications for their horrendous crimes.
Asked by the judge at his trial in 2010 how he could justify planting a bomb in a crowded public place, the "Times Square bomber", Faisal Shahzad, raised the impact of US drone strikes in his native Pakistan that "kill women, children, they kill everybody". Umar Farouk Abdulmutallab, the "underwear bomber" who tried to blow up a US-bound airliner in December 2009, told the judge in his trial that he had worn an explosive device "to avenge the killing of my Muslim brothers and sisters" against "the tyranny of the United States". Then there is Dzhokhar Tsarnaev, the 19-year-old suspect in the Boston Marathon bombings. According to the Washington Post, Tsarnaev "told interrogators that the American wars in Iraq and Afghanistan motivated him and his brother to carry out the attack".
Ah, say the critics, but 9/11 preceded both the invasions of Iraq and Afghanistan and Obama's drone war in Pakistan. They did - but the west's support for Israel's oppression of the Palestinians preceded 9/11. As did the murderous Anglo-American sanctions against Iraq. What did the mastermind of the first al-Qaeda attack on the Twin Towers in 1993, Ramzi Yousef, say at his trial in 1998? "You have [a] so-called economic embargo [on Iraq] which kills nobody other than children and elderly people."
Another tack of the foreign-policy denialists is to smear those who dare mention, say, "Iraq" in the same sentence as "terrorism" as loony lefties or mad Muslims - even though some of the world's top terrorism experts have drawn this connection. "At what point are you going to start listening to the perpetrators who tell you why they're doing this?" Marc Sageman, a former CIA case officer and forensic psychiatrist who has studied more than 500 terrorist biographies, said to me.
The last time I checked, Eliza Manningham-Buller was neither a supporter of the Stop the War Coalition nor a member of the Muslim Council of Britain. Yet the former director of MI5 has said that "our involvement in Iraq, for want of a better word, radicalised a whole generation of young people" and "spurred some young British Muslims to turn to terror". Should we dismiss Manningham-Buller as an "excuse-maker", too?
Even Barack Obama has conceded the link between western policy and Islamist radicalisation. Guantanamo Bay, he said in April, "is a recruitment tool for extremists".
The point is this: terrorism may indeed be a criminal political act but it is a political act nonetheless. It is not, contrary to the conventional wisdom, theologically motivated; according to a leaked MI5 study in 2008, most violent extremists are "religious novices". It is, as Martin Amis once put it, "political communication by other means".
It would be disingenuous of me to claim that foreign policy is the only factor driving radicalisation and extremism, just as it would be naive of me to pretend that terrorist attacks would cease overnight if the US, the UK and their allies stopped bombing, invading and occupying Muslim-majority countries. They wouldn't. There would still be hate-filled, messed up individuals, such as the group of British Islamists who plotted to blow up the Ministry of Sound nightclub in 2004 because of the "slags dancing around" inside, bent on acts of spectacular violence.
Their number, however, would be smaller; anti-western terrorism, as the former head of the CIA's Bin Laden unit Michael Scheuer has argued, would then be "a manageable problem". "I don't think there are a lot of people who want to blow themselves up because my daughters go to university," he told me in 2011. "People are going to... bomb us because they don't like what we've done."
Mehdi Hasan is the political director of the Huffington Post UK and a contributing writer for the New Statesman, where this article is crossposted
Follow Mehdi Hasan on Twitter: www.twitter.com/mehdirhasan