It's been nine years and seven months since Osama bin Laden orchestrated 9/11, but an American team finally killed him. This is revenge, but it's also deterrence and means that bin Laden won't kill any more Americans. This is the single most important success the US has had in its war against al Qaeda.
So what does this mean? First, it's good for the US's reputation, power and influence that we finally got bin Laden. His ability to escape from the US and his apparent impunity fed an image in some Islamist quarters of America as a paper tiger. Moreover, this sends a message that you mess with America at your peril.
That said, killing bin Laden doesn't end al Qaeda. Ayman al-Zawahiri, the Egyptian No 2, has long played a crucial role as al Qaeda's COO. And al Qaeda is more of a loose network than a tightly structured organisation, and that has become even more true in recent years.
AQIM, the version of al Qaeda in North Africa, is a real threat in countries like Mali and Mauritania; killing bin Laden will have negligible consequences there. And Anwar al-Awlaki, the Qaeda-linked terrorist in Yemen, likewise won't be deterred by bin Laden's killing.
It's also true that bin Laden's killing might have mattered more in 2002 or 2003. At that time, in countries like Pakistan, many ordinary people had a high regard for bin Laden and doubted that he was centrally involved in the 9/11 attacks. Over time popular opinion has moved more against him.
Some people still feel respect for his ability to outwit the US, or they are so anti-American that they embrace anybody Americans don't like, but bin Laden has been marginalised over time.
His declining image also means that he won't be a martyr in many circles. His death won't inspire people, the way it might have in 2002. And al Qaeda is already going through a difficult time because it's been sidelined by the Arab Spring protests; on top of that, losing its top leader will be a major blow.
It will be fascinating to see what the Pakistani reaction is to a US military operation on their soil.
President Barack Obama seemed to have gone out of his way to sound deferential to Pakistan precisely because he was concerned that Pakistanis might react with outrage at an American military operation. Of course, this also raises questions about how Osama got to Abbottabad from Afghanistan and what, if anything, the Pakistanis knew.
Former Pakistan President Pervez Musharraf and others always told me and others that Osama was in Afghanistan and even suggested that he might have died. So much for Musharraf.
One question is whether the bin Laden killing will lead to intelligence that will help track down Zawahri and other al Qaeda leaders or operatives, whether in Pakistan or elsewhere in the world. Will there be a reprisal attack by al Qaeda? Maybe. But after all, it's already been trying to hit us. It's not as if it has shown any restraint.
The larger challenge is whether we can press this gain and further dismantle al Qaeda in the Af-Pak region.
If so, it may be easier to end the Afghan war by working out a deal in Afghanistan between the Karzai government and the Taliban; if foreign fighters like bin Laden are out of the picture, an agreement becomes more feasible. Of course, allowing the Taliban a role in southern Afghanistan raises all kinds of questions, not least the impact on Afghan women.
On the other hand, the war is also a catastrophe for Afghan women. And there are some indications that the Taliban are willing to compromise on some elements of policy toward women, such as girls' schooling. That would all have to be negotiated.
Finally, what does this mean for President Obama's political prospects? I don't think very much. November 2012 is a long way away, and the main political issue is likely to be the economy. After all, George HW Bush was a hero after the Gulf War victory in early 1991, and by November 1992 was defeated by Bill Clinton because of the economic slowdown.