The quiet, bespectacled scholar also had careful words of warning: Without achieving this goal, our actions will mean nothing more than mere, repeated disturbances.
Ever since 2011, when Osama bin Laden was killed in a United States raid on his safehouse in Abbotabad, the man who leads al-Qaeda has been trying to extricate his organisation from the rubble of 9/11.
The ferocious US response to the attacks decimated the Islamic state Zawahiri understood held the keys to power and the mantle has since been seized by a successor, the Dawlah Islamiyya, which has decimated al-Qaedas ranks in Iraq and Syria.
In the years he has led it, al-Qaeda has remained a fighting force, represented through powerful regional affiliates that have seized control of swathes of territory from Mali to Libya and Yemen but none have come close to taking control of the state.
The formation of al-Qaeda in the Indian subcontinent could prove a last throw of the dice, with domination of the global Islamist movement as its prize.
In the autumn of 1999, as al-Qaedas influence in Afghanistan reached its peak, Osama bin Laden emerged as a charismatic cult figure for Islamists across the region. That October, seven-year-old Gulrez Siddiqui was reported to have been trotted out in front of 20,000 cheering Students Islamic Movement of India (SIMI) supporters in Mumbai, to read this couplet: Islam ka ghazi, butshikan/ Mera sher, Osama bin Laden (Warrior for Islam, destroyer of idols/ My lion, Osama bin Laden).
The men in the audience included several who would go on to become key figures in the Indian Mujahideen (IM) among them, Riyaz Shahbandri, the groups Karachi-based military commander, and Abdul Subhan Qureshi, a key lieutenant and ideologue.
At another time, the men might have reached out to al-Qaeda but its mind was firmly focussed on a far enemy, the United States of America. Bin Laden believed destroying the US was critical to the advance of Islamism and ignored enemies who cautioned against acts that could lead the US to attack the Islamic emirate ruling Afghanistan.
Following 9/11, much of al-Qaedas second-rung drifted away from Afghanistan, to head affiliates across West Asia. Men like Nasser al-Bahri, bin Ladens bodyguard until the events of 9/11, published memoirs which included an unflattering assessment of al-Zawahiri.
Bin Laden, al-Bahri argued, is a born leader. But Zawahiri had generated a great deal of reserve, sometimes very harsh criticism, he wrote. I doubt he has sufficient authority for such a position, even with his well-known authoritarianism and his penchant for centralizing power in himself.
The Kuwaiti cleric turned al-Qaeda operative, Suleiman Abu Ghaith who appeared in a video broadcast on al-Jazeera weeks after 9/11, proclaiming that the storm of the planes will not stop last year published an online manifesto highly critical of bin Ladens leadership.
Ghaith lashed out at al-Qaeda for taking decisions in haste which led to a big defeat. The poor decision-making, he said, was a consequence of bin Laden being encircled by a bunch of advisers who do not qualify to give advice. He was also critical of al-Zawahiris politics, which had led to isolation of yourself and the mujahideen from the mainstream Islamic movements.
There were many in al-Qaeda who thought the top job should have gone to Ibrahim Makkawi, also known as Saif al-Adel, part of a small caucus of top al-Qaeda commanders, including Saeed al-Masri and Mahfouz Ould al-Walid, who are said to have opposed the 9/11 attacks.
BORN INTO CRISIS
Born into a well-connected upper middle-class family from suburban Cairo, al-Zawahiri was very different from his his critics; an intellectual rather than a fighter. He is said to have excelled as a student, been drawn to poetry, and hated organised sports, seeing them as inhumane.
Drawn to the teachings of the Islamist ideologue Syed Qutb as a teenager, al-Zawahiri joined the Muslim Brotherhood when he was just 14. Qutb, whose works Milestones and In the shade of the Quran are foundational texts for the global Islamist movement, was executed in 1966.
In the years that followed, al-Zawahiri would train as a doctor and specialise as a surgeon. He married Cairo university philosophy student Azza Nowari in 1978; their wedding, held at the Continental Hotel, attracted attention in the liberal Cairo of the times: men were segregated from women, photographers and musicians were kept away, and joking banter was discouraged.
Following the assassination of Egyptian president Anwar Sadat in 1981, Zawahiri was among hundreds arrested and tortured. Released after three years in prison, he fled the country, and began practising medicine in Saudi Arabia. There, he came into contact with Osama bin Laden. He first travelled to visit bin Laden-funded jihad facilities in Pakistan in 1985, a relationship that would slowly mature until 2001, when the Egyptian Islamic Jihad formally merged with al-Qaeda.
The two men became inseparable: the intellectual, serious al-Zawahiri providing the perfect foil to the enthusiastic but politically immature bin Laden. Both men helped plan 9/11; it was to be al-Qaedas greatest moment: a spectacular gesture that would precipitate a civilisational cataclysm between Islam and the west, and signal that the power of the United States was illusory.
Azza, al-Zawahiris wife, and his youngest daughter Aisha would both die in November 2001, pinned under the debris of an al-Qaeda guesthouse hit by American bombs in Afghanistan.
Al-Zawahiri himself would spend the rest of his life trying to clear away the wreckage from around al-Qaeda.
INDIA ON HIS MIND
From 2001, even before 9/11 ignited in Afghanistan, al-Zawahiris mind turned increasingly to India seeing jihad in the subcontinent as a means of destroying the Pakistani state, and expanding the Afghan emirate. His 2001 manifesto proclaimed a religious duty of which the [Muslim] nation had long been deprived, by fighting in Afghanistan, Kashmir, Bosnia-Herzegovina and Chechnya. From 2011, when he took charge of al-Qaeda, building a subcontinental front to wage jihad began to become an operational objective.
The idea had been touched upon by bin Laden himself in 1996, when he issued a declaration condemning massacres in Tajikistan, Burma, Kashmir, Assam, the Philippines, Pattani, Ogaden, Somalia, Eritrea, Chechnya, and Bosnia-Herzegovina.
Later, in September 2003, al-Zawahiri invoked India to warn Pakistanis that their President, General Pervez Musharraf, was plotting to hand you over to the Hindus and flee to enjoy his secret accounts.
From that time on, al-Zawahiri expanded contacts with Muhammad Illyas Kashmiri, the leader of Brigade 313, a jihadist unit that draws its name from the number of soldiers who fought alongside the Prophet to defeat the numerically superior armies of pagan Mecca.
Incensed at Musharrafs betrayal of the Pakistan armys long-standing jihadist allies, al-Zawahiri set up base in North Waziristan, and began waging war against the state.
In 2010, evidence of Kashmiris global ambitions began to become evident. 26/11 perpetrator David Headley gave evidence of his plot to target the Jyllands Posten newspaper in Denmark. The following year, German nationals Shabab Dasti and E Bnyamnin, along with their French counterpart Naamen Meziche all recruited from an Islamist-controlled Hamburg mosque once used by the 9/11 hijackers were killed in a drone strike, while plotting attacks in Europe based on Kashmiris directions.
Thursdays declaration of a subcontinent-wide jihad comes after years of contact between elements of the Indian Mujahideen and al-Qaeda, first set up by Illyas Kashmiri. In recent years, National Investigation Agency officers who have questioned alleged Indian Mujahideen operatives say members of the group have met with al-Qaeda to discuss joint operations.
There has also been at least one case of an Indian dying in combat with al-Qaeda affiliated groups in Afghanistan Anwar Bhatkal, who died in an attack on an outpost in Kandahar last month, first reported in The Indian Express.
It is impossible to say if al-Zawahiris plan for subcontinental jihad will bring al-Qaeda back to the Islamist centre-stage but it is certain that blood will be spilt in the effort.