(CNN) -- Ten years after the devastating attacks on America, Defense Secretary Leon Panetta recently said the United States is "within reach of strategically defeating al-Qaeda."
His comments came after the successful joint U.S. intelligence and military operation in May that led to the death of number one terrorist Osama Bin Laden, and the intensified effort over the past several years to wipe out senior al Qaeda operatives through drone missile strikes.
"I do believe that if we continue this effort that we can really cripple al Qaeda as a threat to this country," Panetta said.
Still, there are a significant number of names on the U.S. list of wanted terrorists.
CNN spoke with a number of intelligence agencies to come up with a list of the dirty dozens: the 12 most significant terrorists who are now dead, who have been captured and who are still being hunted. The lists are obviously subjective -- there are many more candidates -- but these are some of the top combatants in the war on terror.
An American-born Muslim cleric who advocates violent jihad against the United States, al-Awlaki died in an airstrike in Yemen on Friday, a Yemeni government official said. He has been connected to two of the 9/11 hijackers as well as the accused Fort Hood shooter Maj. Nidal Milik Hasan and suspected underwear bomber Umar Farouk AbdulMutallab. He was considered an operational leader of al Qaeda in the Arabian Peninsula, or AQAP, in Yemen.
Osama bin Laden
Founder and leader of al Qaeda, responsible for the September 11, 2001 attacks against the United States as well as numerous other mass-casualty attacks. U.S. Navy Seals killed bin Laden during a raid on his compound in Abbottabad, Pakistan in May 2011.
He was a founding member and military chief of al Qaeda. A U.S. airstrike killed him during early fighting in Afghanistan in November 2001.
Abu Musab al-Zarqawi
A militant jihadist who opposed U.S. presence in the Middle East, al-Zarqawi had a profound hatred for Israel. He formed his own terrorist group, Tawhid wal-Jihad. In 2004, he pledged alliance to al Qaeda and changed the name of his group to al Qaeda in Iraq. He was responsible for hundreds of attacks in Iraq. U.S. bombs killed Zarqawi in Iraq in June 2006.
Abu Layth al-Libi
This senior al Qaeda military commander planned attacks against U.S. and coalition forces in Afghanistan, including a 2007 bombing of the Bagram Air Base during a visit by then Vice President Richard Cheney. He was killed in a drone attack in Pakistan in March 2008.
Atiyah Abd al-Rahman
Until his recent death, he was the number two to al Qaeda leader Ayman al-Zawahiri and a key facilitator with al Qaeda affiliates. Materials seized in the Bin Laden compound showed al-Rahman was in frequent contact with bin Laden. A drone strike in Pakistan killed him in August 2011.
Abu Hamza Rabia
An operational planner for attacks against the United States, he died in a drone strike in Pakistan in November 2005. Abu Hamza Rabia replaced Muhammad Atef as al Qaeda's military chief after Atef's death in 2001.
Abu Ayyub al Masri
Replaced Abu Musab al-Zarqawi as leader of al Qaeda in Iraq and the insurgency in Iraq. U.S.and Iraqi forces killed him in a joint operation in April 2010.
Sayeed al-Masri (also known as Abu Shaykh Mustafa Abu al-Yazid)
Once number three in the al Qaeda hierarchy, al-Masri was the commander of operations in Afghanistan and Pakistan and the group's chief financial officer. He died in drone strike in Pakistan in May 2010.
Mohammad Hasan Khalil al-Hakim
The senior operational manager, deputy chief of external operations and head of propaganda for al Qaeda, he died in a drone strike in Pakistan in October 2008.
Abu Khabab al-Masri (also known as Midhat Mursi)
Al Qaeda's chief bomb-maker and chemical-weapons expert, a drone attack in Pakistan killed him in July 2008.
Abu Obeidah al Masri
This senior al Qaeda operative, who was implicated in the 2006 plot to bomb commercial airliners after take-off from London, died of natural causes in December 2007.
Fazul Abdullah Muhammed
The leader of al Qaeda operations in East Africa, he is believed to have been involved in the 1998 bombings of the U.S. embassies in Kenya and Tanzania. He was killed in Somalia in June 2011.
Khalid Sheikh Mohammed
The operational planner and mastermind of the 9/11 attacks, Mohammed was captured in Pakistan in March 2003. The United States is holding him at its detention center in Guantanamo Bay, Cuba.
Abu Faraj al-Libi
He replaced Khalid Sheikh Mohammed after Mohammed's capture and directed operations against U.S. and coalition forces in Afghanistan. He planned the 2003 assassination attempt against then-Pakistani President Pervez Musharref. He was captured in May 2005 and is being held at the U.S. military detention center in Guantanamo Bay, Cuba.
Ramzi Bin al-Shibh
Involved in planning the 9/11 attacks, al-Shibh associated with some of the 9/11 hijackers. He is believed to have been designated as the 20th hijacker that day, but he could not get into the United States. He was captured in September 2002 and is held at the U.S. military detention center in Guantanamo Bay, Cuba.
Initially believed to be a high-ranking al Qaeda leader, the U.S. later concluded that he held a much lower position. He was captured in Pakistan in March 2002 and is held at the U.S. military detention center in Guantanamo Bay, Cuba.
Investigators have connected Patek to the 2002 Bali nightclub bombing, which killed more than 200 people, including 7 Americans. He was captured by Pakistani forces in January 2011 and sent to Indonesia.
A key planner for al Qaeda, he is believed to have had direct contact with Osama bin Laden and was involved in planning attacks in Europe. Pakistani forces captured him in September 2011. The Pakistani government is holding him.
Hambali (also Riduan Isamuddin)
As the operations chief for the terrorist group Jemaah Islamiya, he has often been described as bin Laden's leader in Southeast Asia and is believed to have been connected to a number of deadly bombing attacks in Indonesia. He was captured in a joint U.S -Thai operation in Thailand in August 2003. The United States is holding him at its detention center in Guantanamo Bay, Cuba.
Al Rahim al Nashiri
He was the head of al Qaeda operations in the Persian Gulf and believed to be the mastermind of the bombing of the USS Cole in 2000 in which 17 U.S. sailors died. He was captured in November 2002. The United States is holding him at its detention center in Guantanamo Bay, Cuba.
Ali al Aziz Ali
Khalid Sheikh Mohammed's nephew and chief deputy, he helped train some of the 9/11 hijackers. He was captured in April 2003. The United States is holding him at its detention center in Guantanamo Bay, Cuba.
Walid bin Attash
Former bin Laden body guard, he assisted the 9/11 hijackers, helped with preparations for the 1998 bombings of the U.S. embassies in East Africa and the 2000 attack on the USS Cole. He was captured in April 2003. The United States is holding him at its detention center in Guantanamo Bay, Cuba.
Mustafa Ahman al Hawsawi
He worked with Khalid Sheikh Mohammed on numerous al Qaeda plots, including providing assistance to 9/11 hijackers. He was captured with Khalid Sheikh Mohammed in March 2003 in Pakistan. The United States is holding him at its detention center in Guantanamo Bay, Cuba.
Abdul Ghani Baradar
A founder of Afghan Taliban and deputy to leader Mullah Omar, he directed the insurgency against U.S. and coalition forces from Pakistan. Pakistani and American intelligence forces captured him in February 2010. He is in Pakistani custody.
A physician and long-time deputy to Osama bin Laden, he was named leader of al Qaeda following bin Laden's death. He has been seen and heard in numerous al Qaeda videos and audio tapes on the web. He is on the FBI Most Wanted Terrorists list and a U.S. grand jury indicted him over his role in the 1998 bombings of the U.S. embassies in Kenya and Tanzania.
A member of the senior leadership of al Qaeda who is believed to be in Iran, he is on the FBI Most Wanted Terrorists list. Al-Adel is under indictment in the United States over the 1998 bombings of the U.S. embassies in Kenya and Tanzania.
A computer expert for al Qaeda who is on the FBI's Most Wanted Terrorists list, al-Liby has been indicted for his role in the 1998 bombings of the U.S. Embassies in Kenya and Tanzania.
Adnan el Shukrijumah
A senior leader of al Qaeda's external operations program who is on the FBI's Most Wanted Terrorists list, a U.S.grand jury indicted him over a 2009 plot to attack the New York subway system as well as targets in the United Kingdom.
A leader of the Pakistan Taliban with close ties to al Qaeda and the Afghan Taliban, he claimed responsibility for the 2009 bombing at the Khost Forward Operating Base in Afghanistan, which killed 7 CIA employees. He is on the FBI's Most Wanted Terrorists list.
Abu Yahy al-Libi
An Islamic scholar and high-ranking member of al Qaeda, al-Libi is often seen as the public face of the organization. He frequently appears in internet videos.
He is the American propagandist for al Qaeda who is frequently seen on al Qaeda website videos. A grand jury in California indicted him on charges of treason and material support to al Qaeda, and he is on the FBI Most Wanted Terrorists list.
Mullah Mohammad Omar
As leader of the Taliban in Afghanistan, Omar gave Osama Bin Laden and al Qaeda safe haven prior to the 9/11 terrorist attack on the United States and the subsequent U.S. invasion.
Nasser Al Wahishi
The leader of al Qaeda in the Arabian Peninsula, or AQAP, and the former private secretary to Osama Bin Laden, al Wahishi has vowed to avenge the former al Qaeda leader's death.
A senior leader of the Haqqani network in Afghanistan, which maintains close ties to al Qaeda, Haqqani is believed to have planned an assassination attempt against Afghanistan President Hamid Karzai.
Wali Ur Rehman
He is a senior member of the Pakistani Taliban who has participated in cross-border attacks against U.S. and coalition forces in Afghanistan.