Final answer:
The U.S. gained substantial insight into Al-Qaeda after the September 11, 2001, attacks, following their military intervention in Afghanistan and the eventual killing of Osama bin Laden in 2011.
Step-by-step explanation:
The United States first got an inside look at Al-Qaeda following the September 11, 2001, terrorist attacks. Al-Qaeda, under the leadership of Osama bin Laden, carried out the attacks leading to the U.S. launching Operation Enduring Freedom. This military action in 2001 aimed to dismantle Al-Qaeda's training camps and remove the Taliban from power in Afghanistan, providing the U.S. with critical intelligence on the terrorist organization. America's view into Al-Qaeda was further extended post-invasion as they rebuilt Afghan civil society and supported a democratic regime.
Osama bin Laden initially received support from the U.S. during the Soviet-Afghan War but later became a staunch opponent of the West. Post the 9/11 attacks, despite efforts, bin Laden eluded capture for years until May 1, 2011, when he was located and killed by U.S. special forces in Pakistan. This moment was pivotal, raising questions about the extent of regional support for Al-Qaeda and providing a hopeful sign for the decline of terrorism.