It has been almost a year since June 29, 2014, when the Islamic State of Iraq and al-Shams (ISIS) declared the formation of a new caliphate and dropped the second half of its name, rebranding itself as simply the Islamic State. It has survived nine months since Barack Obama vowed to “degrade and ultimately destroy” it.

It has survived, and has continued to attract Muslims from all over the world, even after virtually every major world leader and Islamic group has condemned it as un-Islamic. And it shows no sign of going anywhere anytime soon.

All this is well-known. What is less known is that the plan for the restoration of the caliphate was sketched out ten years ago by al-Qaeda leader Ayman al-Zawahiri, and has been followed out more or less exactly by the Islamic State.

The claim to reconstitute the caliphate is the key to the Islamic State’s success — the importance of this cannot be overstated.

The revival of the caliphate is, in the eyes of those who support it and have longed for it all these years, a return to the form of government of the glory days of Islam. From Muhammad’s death through Islam’s Golden Age up until the breakup of the Ottoman Empire after the end of World War I, Muslims were ruled by a caliph, the successor to Muhammad as spiritual and political leader of Islam.

And the declaration of the caliphate, and its placement in and around Syria and Iraq, was not an invention of the Islamic State, or incidental to what it perceived as its mission from the beginning. In reality, a new caliphate had long been an aspiration dear to the hearts of many jihadi terrorists, including al-Qaeda.

Bin Laden’s lieutenant Ayman al-Zawahiri wrote to the leader of al-Qaeda in Iraq (which ultimately became the Islamic State), Abu Musab al-Zarqawi, on July 9, 2005:
It has always been my belief that the victory of Islam will never take place until a Muslim state is established in the manner of the Prophet in the heart of the Islamic world, specifically in the Levant, Egypt, and the neighboring states of the Peninsula and Iraq; however, the center would be in the Levant and Egypt.
Zawahiri also heaped praise on Zarqawi for helping bring that state — the revived caliphate — closer to reality:
If our intended goal in this age is the establishment of a caliphate in the manner of the Prophet and if we expect to establish its state predominantly — according to how it appears to us — in the heart of the Islamic world, then your efforts and sacrifices — God permitting — are a large step directly towards that goal.
Zawahiri then offered Zarqawi his “humble opinion that the Jihad in Iraq requires several incremental goals,” the first of which was to “expel the Americans from Iraq.” The second stage, wrote Zarqawi, would be exactly what the Islamic State ended up doing nine years later:
The second stage: Establish an Islamic authority or amirate, then develop it and support it until it achieves the level of a caliphate — over as much territory as you can to spread its power in Iraq, i.e., in Sunni areas, is in order to fill the void stemming from the departure of the Americans, immediately upon their exit and before un-Islamic forces attempt to fill this void, whether those whom the Americans will leave behind them, or those among the un-Islamic forces who will try to jump at taking power.
Following the establishment of this state, the third stage would be to “extend the jihad wave to the secular countries neighboring Iraq,” followed by the fourth stage, which “may coincide with what came before: the clash with Israel, because Israel was established only to challenge any new Islamic entity.”