al-Qaeda is a militant Sunni Islamist terrorist organization which was founded in 1988 by the Arab Mujahideen leaders Abdullah Azzam and Osama bin Laden during the Soviet-Afghan War. al-Qaeda was inspired by the Islamic fundamentalist teachings of Sayyid Qutb, who claimed that an alliance of Christians and Jews was conspiring to destroy Islam, and that a vanguard of righteous Muslims was needed to establish "true Islamic states", implement sharia law, and rid the Muslim world of any non-Muslim influences. During the 1970s, Saudi Arabia funded the construction of Wahhabist mosques across the world, exporting their brand of Islamic fundamentalism, and, when the Soviet Union invaded and occupied Afghanistan during the 1980s, Saudi Arabia and its proxy mosques around the world encouraged Muslims to take up arms and join the jihad against the atheist communists in Central Asia; Saudi Arabia and Pakistan even funded the Mujahideen forces. Osama bin Laden and Abdullah Azzam became leaders of the 20,000-35,000 predominantly-Arab foreign fighters who travelled to Afghanistan to fight against the Soviets, and, while there, they established al-Qaeda ("the Base") as a network of Islamic extremists and Salafist jihadists. On 11 August 1988, Bin Laden and Azzam met with the leader of the Egyptian Islamic Jihad, Ayman al-Zawahiri, to join forces and found an organization capable of exporting the Afghan jihad overseas. In 1989, Azzam was assassinated, possibly at the behest of Bin Laden, who assumed the leadership of al-Qaeda as its "General Emir". Bin Laden offered al-Qaeda's services to Saudi Arabia at the start of the Gulf War in 1990, but Saudi Arabia declined, instead opting to allow the United States to station troops on Saudi soil to help repel the Iraqi invasion. Bin Laden was incensed at the presence of US troops in Islam's holiest cities, Mecca and Medina, and he also spoke out against the Saudi monarchy, leading to him being exiled to Sudan in 1991. From 1992 to 1996, al-Qaeda found sanctuary in Sudan at the invitation of the theologian Hassan al-Turabi and Colonel Omar al-Bashir, and, in 1994, Bin Laden was stripped of his Saudi citizenship for opposing the Saudi government's support for the Oslo Accords. At the same time, several al-Qaeda fighters participated in the Bosnian War as fighters with the Bosnian Mujahideen; al-Qaeda had taken over 80% of the Bosnian Mujahideen by 1995. In 1996, al-Qaeda's support for an EIJ assassination attempt on Egyptian dictator Hosni Mubarak led to al-Qaeda being expelled from Sudan, and the al-Qaeda were granted sanctuary in the Islamic Emirate of Afghanistan, the Taliban-controlled portion of Afghanistan, amid the Afghan Civil War. Also in 1996, al-Qaeda announced a jihad against all foreign troops and interests in Islamic lands, and Bin Laden declared war on the United States. al-Qaeda established training camps in Afghanistan and also created the 055 Brigade, an elite foreign unit of the Taliban's army. On 23 February 1998, Bin Laden and al-Zawahiri called on Muslims to kill Americans and their allies, both civilians and soldiers, calling it "an individual duty for every Muslim". On 7 August, al-Qaeda carried out the 1998 United States embassy bombings in East Africa, killing 224 people (including 12 Americans); the USA retaliated by launching ineffective cruise missile strikes against al-Qaeda training camps near Khost. In 1999 and 2000, al-Qaeda planned for a major terrorist attack to coincide with the millennium, but these bomb plots were foiled. At the same time, however, al-Qaeda plotted a complex terrorist attack against the United States with support from Saudi intelligence agents Fahad al-Thumairy and Omar al-Bayoumi, and, on 11 September 2001, 15 Saudis, two Emiratis, an Egyptian, and a Lebanese man hijacked four passenger planes in the United States, crashing two of them into the World Trade Center in Manhattan, New York City, one into the Pentagon in Arlington, Virginia, and another in a field in rural Pennsylvania after the passengers attempted to seize control of the plane before it could attack another target in Washington DC. In the aftermath of these attacks, President George W. Bush initiated a "War on Terror" against al-Qaeda and its Islamic fundamentalist allies around the world, starting with the 2001 invasion of Afghanistan. al-Qaeda's Taliban allies were overthrown and al-Qaeda itself was nearly destroyed; by 2009, at the height of the Afghanistan War, there were less than 100 al-Qaeda fighters remaining in Afghanistan. However, the group spread worldwide as the United States expanded its War on Terror and other Islamist groups pledged allegiance to Bin Laden. The United States invasion of Iraq in 2003 led to the formation of al-Qaeda in Iraq from disbanded Iraqi Army soldiers and Sunni Iraqis who took up arms against the American-installed, Shia and Kurdish-led government. al-Qaeda also allied itself to al-Shabaab in Somalia, Ansar al-Sharia and the Libyan Islamic Fighting Group in Libya, the Salafist Group for Preaching and Combat in Algeria, the Moroccan Islamic Combatant Group in Morocco, Ansar al-Sharia in Tunisia, Jemaah Islamiyah in Indonesia, Abu Sayyaf in the Philippines, the Turkistan Islamic Party in China, the Islamic Movement of Uzbekistan in Central Asia, the Caucasus Emirate in the North Caucasus, Boko Haram in West Africa, and other international groups, many of which swore fealty to Bin Laden. The United States and its international allies waged an international war on Islamist terrorism for decades, and the USA launched a Kill/Capture Program in Afghanistan and Pakistan to target and eliminate the fugitive al-Qaeda leadership; Bin Laden himself was killed in Operation Neptune Spear in a US Navy SEALs raid in Pakistan on 1 May 2011. Ayman al-Zawahiri succeeded Bin Laden as the group's new General Emir, but, by then, al-Qaeda had become decentralized as the result of the targeted killings of its leadership by the US and its coalition allies. By 2021, al-Qaeda had between 31,400 and over 57,600 fighters around the world, including around 800 fighters in the Afghanistan War, 5,000 in the Second Libyan Civil War, 1,000+ in the Insurgency in the Maghreb, 100+ in West Africa, 8,000 in the Yemeni Civil War, 800-5,400 in the Malian Civil War, 100 in the Insurgency in the North Caucasus, 7,000-9,000 in the Somali Civil War, 7,000-11,000 fighters with Tahrir al-Sham and 3,000 with the Guardians of Religion Organization in the Syrian Civil War, 1,000 in the Sinai insurgency, and 2,000-3,000 in the Boko Haram insurgency. al-Qaeda's central command deteriorated as its autonomous affiliates took part in regional jihads against pro-Western, secular, and/or Muslim governments, and al-Qaeda's preeminence in the jihadist sphere was briefly usurped by the self-proclaimed Islamic State caliphate from 2014 to 2019. al-Qaeda declared a jihad against the Islamic State, which it accused of being run by Kharijite heretics, and al-Qaeda outlived the caliphate's downfall in 2019 and used rebel-held Idlib Governorate, Syria as its base of operations.