Five years on from 9/11, BBC journalist Peter Taylor has been investigating the effect of the "War on Terror" on young Muslims.
In the first of two special programmes, he revealed how the US and UK governments are in denial over how their policies may have been contributing factors.
Here, he answers some of your questions.
Q: Are the Islamic fundamentalists trying to force their religion on the rest of the world?
Mike Allen, Preston
Some of them undoubtedly are. Although the Caliphate - a pan-Islamic state under Sharia law - is their ultimate goal, their more immediate aim is through their attacks to force America to change its foreign policy since they see it as an attack on the Muslim global community known as the "Ummah".
Q: What do these terrorists actually want?
G Andrew Holmes, Norwich
Bin Laden wants three things: an end to US support for Israel; the removal of foreign (ie US) troops from the Middle East; and a severance of US support for the authoritarian regimes in the region. In the end, he also wants a Caliphate, but this is rarely mentioned in his utterances. Interestingly in his letter to the American people, posted on the internet in October 2002, he also invited America to "deal with us and interact with us on the basis of mutual interest and benefits".
Q: What do radicalised young British Muslims do when they get to Iraq? Do they want to fight against US/British forces? Do they want to join sectarian groups? Or do they want to join the "insurgents"?
Effie Romain, Bristol
Most go there to fight the coalition forces whom they see as "invaders" of Muslim lands. Their aim is to die fighting as "martyrs" - "shaheeds" but not necessarily as suicide bombers. Most, I suspect, would not go to blow up Shia Muslims, however much Sunni Muslims regard them as "apostates".
Q: America's uncritical support of Israel has been cited as one of the main factors that has angered Muslims over many years. Do you consider this to be true?
Kevin Twiggs, South Africa
Yes - in addition to the other issues mentioned above.
Q: How are we to weed out the extremists in our midst without upsetting the moderate Muslims who reside in every Western country?
The $64,000 question. The intelligence services are very conscious of the need to keep the majority of the Muslim community onside. After all, the majority have no connection with terrorism and they remain a critical source of intelligence for the intelligence agencies. Raids like Forest Gate in east London don't help. The police also have to come up with the evidence to justify their actions.
Q: Have media images of atrocities, arising from the US-led invasion of Iraq, helped the radicalisation of Muslims? Should these be restricted?
They have no doubt helped and are a powerful radicalising tool for al-Qaeda and its allies via the internet. No, they should not be restricted in a free society.
Q: Do you feel a radical Islamist agenda already existed with a purpose well before 9/11 and that subsequent US foreign policy in concert with the UK may have fuelled this agenda further, or do you feel without the Iraq intervention post 9/11 the Islamist radicalisation would simply not exist today?
H Patel, Shirley
Yes, it existed well before Iraq and really emerged in the early-to-mid 1990s - post Afghanistan. Iraq has just played into Bin Laden's hands as I illustrated in my first programme.
Q: Do you think there's a risk that popular anti-war sentiment among the public at large is being hijacked to justify extremism by some?
Graeme Priest, Bristol
No. As I tried to outline in the film, I believe that Iraq is a deeply felt reason for radicalisation and not an excuse.
Q: From watching the violence in Iraq it is obvious that most, if not all, of the killing is Muslims killing other Muslims. How can this violence be blamed on the occupying forces?
Matthew Smith, Manchester
It can't. It's being deliberately encouraged by al-Qaeda in Iraq to foment civil war so Iraq becomes ungovernable and America is humiliated.
Q: I would like to know why Peter Taylor thinks it is possible to talk to al-Qaeda? What on earth could we possibly talk to them about?
Richard Mottershead, Southport
I didn't argue that it makes sense to talk to al-Qaeda but that it was an option we should consider. And there's a question mark. Looking at the historical precedence for governments talking to terrorists, the conclusion I reached is that although talking via back channels to al-Qaeda is not really on the agenda at the moment, what it is worth doing is looking at what al-Qaeda actually wants and considering the sort of political implications of the messages.
If you look at the history of the Irish peace process, where MI6 and MI5 had back channels via intermediaries to the so-called terrorists at the time, it is not inconceivable that at some stage, and that stage is not now, that there may be similar contacts via intermediaries to the leadership of al-Qaeda.
Al-Qaeda: Turning the Terrorists will be broadcast on BBC 2 on Wednesday 13 September at 2100 BST.