On the morning of September 11, 2001, 19 hijackers affiliated with the international terrorist network al Qaeda carried out a string of attacks that took the lives of nearly 3,000 people. In the 11 years that passed since the tragic events of 9/11, al Qaeda underwent some dramatic transformations.

The U.S. war in Afghanistan has reduced the group's power base in Afghanistan, while affiliates in west Africa and Yemen have gained in strength. Al Qaeda forged alliances with the Somali militant group al Shabab, carrying out deadly attacks in London and Madrid.

Yet many of al Qaeda's leaders have been captured or killed. According to CNN's Peter Bergen, CIA drone strikes have killed 15 of the most important players in al Qaeda under president Obama, while 16 key al Qaeda operatives in Pakistan were killed during the George W. Bush presidency. The terrorist network lost its longtime leader Osama bin Laden in a U.S. raid on May 1, 2011, as well as its deputy Yahya al Libi in June 2012.

HuffPost World takes a look at al Qaeda's leadership, 11 years after 9/11. Who's still in power? Find out in the slideshow below:

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  • Osama Bin Laden

    Al Qaeda's longtime leader <a href="http://www.huffingtonpost.com/2011/05/01/osama-bin-laden-dead-killed_n_856091.html" target="_hplink">was killed</a> in an American raid on his compound in the Pakistani city of Abbottabad on May 1, 2011. (AP Photo, File)

  • Ayman al Zawahri

    Ayman al Zawahri became <a href="http://www.foxnews.com/us/2012/04/29/5-most-wanted-al-qaida-leaders/" target="_hplink">al Qaeda's new leader</a> after the death of Osama bin Laden. He is believed to be hiding in Pakistan and regularly releases propaganda videos. (AP Photo/SITE Intel Group)

  • Abu Yahia al Libi

    Abu Yahia al Libi was al Qaeda's <a href="http://www.huffingtonpost.com/huff-wires/20120429/us-al-qaida-top-5/" target="_hplink">de facto no. 2</a> after the death of Bin Laden. He escaped a high-security U.S. prison in Bagram, Afghanistan, in 2005. Al Libi <a href="http://www.huffingtonpost.com/2012/06/05/abu-yahia-al-libi-drone-strike_n_1569772.html" target="_hplink">was killed</a> in a drone strike in Pakistan in June 2012. (AP)

  • Nasser al Wahishi

    Al Wahishi was once bin Laden's <a href="http://www.huffingtonpost.com/huff-wires/20120429/us-al-qaida-top-5/" target="_hplink">aide-de-camp</a> and now commands AQAP, al Qaeda's affiliate in the Arabian Peninsula. (AFP/GettyImages)

  • Ibrahim Hassan al Asiri

    Saudi Ibrahim Hassan al Asiri is <a href="http://www.huffingtonpost.com/huff-wires/20120429/us-al-qaida-top-5/" target="_hplink">believed to be responsible </a>for building the underwear bomb used to try to bring down a Detroit-bound jetliner on Christmas 2009, as well as the printer-cartridge bombs. (AP)

  • Said al Masri

    Al Qaeda's no. 3 was <a href="http://www.huffingtonpost.com/2010/05/31/al-qaeda-number-three-reported-killed_n_595561.html" target="_hplink">killed</a> in an American drone strike in May 2012. (Reuters TV)

  • Fazul Abdullah Mohammed

    Mohammed, who led the organization in Eastern Africa, was <a href="http://www.huffingtonpost.com/2011/06/11/fazul-abdullah-mohammed-dead_n_875363.html" target="_hplink">killed</a> by the Somalian army in June 2011. (AP)

  • Abu Musab al Zarqawi

    Al Qaeda's brutal leader in Iraq was <a href="http://www.huffingtonpost.com/2010/04/19/two-top-al-qaeda-figures-_n_542653.html" target="_hplink">killed</a> in a U.S. airstrike in 2006. (AP Photo/U.S. Department of State, HO)

  • Khalid Sheikh Mohammed

    Khalid Sheikh Mohammed, the <a href="http://www.huffingtonpost.com/2012/05/06/khalid-sheikh-mohammed-trial_n_1489527.html" target="_hplink">self-described mastermind</a> of the attacks of 9/11, was <a href="http://www.bbc.co.uk/news/world-12964158" target="_hplink">captured in Pakistan in March 2003</a> and is currently being held at Guantanamo Bay. (AP Photo/FBI) <em><strong>CORRECTION:</strong> An earlier version of this slide misstated the date of Sheikh Mohammed's capture.</em>

  • Saif al Adel

    Al Adel was Bin Laden's former <a href="http://www.huffingtonpost.com/huff-wires/20120229/ml-egypt-arrest/" target="_hplink">security advisor</a>. He is still on the run. (Getty Images)

  • Adnan el Shukrijumah

    Adnan El Shukrijumah is reportedly responsible for al Qaeda's external operations. He <a href="http://www.huffingtonpost.com/2010/08/06/adnan-shukrijumah-new-al_n_673164.html" target="_hplink">lived in the U.S.</a> for more than 15 years. (FBI)

  • Atiyah Abd al Rahman

    Al Rahman was al Qaeda's liaison for Iraq, Iran and Algeria until he <a href="http://www.huffingtonpost.com/2011/08/27/atiyah-abd-al-rahman-al-qaeda-dead_n_939009.html" target="_hplink">was killed</a> on August 22, 2011 in Pakistan. (AP Photo/National Counterterrorism Center)

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