In 2006, Ayman Al Zawahiri, often described as the brains behind Al Qaeda, released one of his many video addresses, this one titled "A Message to the People of Pakistan". In it he calls on them to fight their government, labels the leaders of a number of Arab countries traitors, including in his native Egypt, and says that his group has "broken the back" of America in Iraq. It represents both the aspirations of Al Zawahiri and the threat of Al Qaeda in that era, arguably the most notorious global terror group ever to have existed.
During his time in the organisation, thousands were killed by its operatives, in places as diverse as New York, Aden, Nairobi, Baghdad, Madrid and Riyadh, to name only a few. While its declared intention was to wreak havoc in the non-Islamic world, Muslim and Arab countries were major victims of Al Qaeda's terror.
And the group was indeed an elusive thorn in the side of the US military for many years. That finally changed in 2011, when American special forces killed its leader, Osama bin Laden. More than a decade on, Al Zawahiri has now met the same fate – although this time from the sky – following a US missile strike on a location in which he was staying in Afghanistan.
Speaking of the killing, US President Joe Biden said: "Justice has been delivered. This terrorist leader is no more."
There is a great deal of interest among military analysts as to how this “justice was delivered”. There is much speculation that it came from Washington’s "flying Ginsu" R9X variant of the Hellfire missile. The projectile is designed to kill individuals, not groups, therefore supposedly protecting innocent bystanders. US officials have insisted that no one else was killed in the strike.
While this is welcome, it is important to remember that we are not yet in the era, if we ever will be, of drone strikes that guarantee the safety of civilians. The last known US strike in Afghanistan killed 10. And in the wider, decades-long and complicated fight against Al Qaeda, many innocent people have died.
The timing of the deaths of Al Qaeda's two most senior operatives is strangely precise. Ten years after 9/11, the group's most consequential attack, the US killed Bin Laden. Now, more than 10 years after that, his group's second-most important leader is dead.
However, what happened in between these milestones is anything but ordered. US warfare against terrorists has changed, favouring distant strikes over longer-term attempts to provide economic or social development to regions where terrorists thrive, and deal with the grievances that have led to many people falling under their sway. Afghanistan, where Al Zawahiri was killed, is in the control of the Taliban, a group that has a history of sheltering Al Qaeda and working closely with it. This follows the US's disastrous withdrawal from the country almost a year ago. Crucially, new groups have emerged, which are now far better known than Al Qaeda.
Finally, even the justice that Mr Biden speaks of is lacking. From the Guantanamo Bay detention camp to secretive drone strikes, the way US-led payback has come is anything but transparent. True justice would have seen Al Zawahiri in court.
Despite his far lower profile in recent years, the world is safer without him. But, in part due to conditions created by the war on terror, he will by no means be that last terrorist to threaten the world. The long road towards his killing is full of lessons that should be learnt.