A year after the start of the US-led invasion of Iraq, the BBC's security correspondent, Frank Gardner looks at the repercussions of that war on the international security situation.
One of the criticisms of the was in Iraq is that it has made the world a more dangerous place. Is this correct?
In the short term, yes. The US-led invasion and subsequent occupation of a sovereign Arab country has provided a rallying point for those who see the West as neo-colonialists bent on oppressing Muslims and controlling Arab oil reserves.
While this is by no means a universal viewpoint in the Arab world, such suspicions have helped al-Qaeda's recruiting and extended their support base.
Iraq is a dangerous mess and many Arabs blame the West
On the other hand, the war has removed any possibility that Iraq could have become a nuclear nation in the future with Saddam Hussein and his brutal sons having their fingers on the button.
Can we be sure we are seeing al-Qaeda's hand behind the attacks in Iraq?
No, we can't, although it looks increasingly likely that there is some cooperation between Islamist militants who fought in Afghanistan and local Iraqis violently opposed to the US military and its Iraqi allies.
There have also been a number of statements purporting to come from al-Qaeda which claim responsibility for major attacks in Iraq, and which threaten more.
What does this mean for the Middle East as a whole?
Arab regimes, especially those in the Gulf, generally dislike instability. This is why they were so concerned at the potential consequences of a US invasion of Iraq.
Now, one year on, they face several problems. These include small sections of their youth wanting to volunteer to fight the Americans in Iraq, and those young men, in turn, making links with local Islamists sympathetic to al-Qaeda; enormous pressure from Washington to reform and democratise; and a revival of old Sunni-Shia rivalries given the latter's newfound powers in Iraq.
One year on, what can we say about the success or otherwise of the "war on terror"?
It's a misleading term, because due to the ideological nature of the al-Qaeda movement this is not a war that can ever be definitively won or lost.
The West's early successes in depriving al-Qaeda of its physical bases in Afghanistan in 2001, then freezing suspect bank accounts, have given way to a growing realisation that the global threat of terrorism could be with us for decades.
Counter-terrorism intelligence co-operation between and within nations has improved enormously. But the bombings in Istanbul and Madrid prove that Islamic militants, whether linked to al-Qaeda or not, still have the capability to inflict massive death tolls.
Is there another way, or other ways, to prosecute this "war"?
The Pentagon, which is the main driving force behind the US-led "war on terror", has naturally tended to focus on military successes, including the killing or capture of key al-Qaeda figures.
But nearly every analyst agrees that not enough is being done to tackle al-Qaeda's popularity, which stems from a widespread Muslim disenchantment with both the US and its government allies in the region.
The lost opportunity of not planning properly for a swift victory over Saddam Hussein has had disastrous consequences for the West. Iraq is still a dangerous mess and Arabs blame the West.