The "9" in your query likely refers to the September 11, 2001 terrorist attacks (commonly known as 9/11). They were carried out by 19 hijackers from the Islamist extremist group al-Qaeda, who hijacked four commercial airplanes and used them as weapons to attack key targets in the United States: two planes flew into the Twin Towers of the World Trade Center in New York City, one into the Pentagon in Arlington, Virginia, and the fourth crashed in Pennsylvania during a passenger revolt. The reasons behind the attacks were rooted in multiple geopolitical and ideological motives expressed by al-Qaeda leader Osama bin Laden. These included opposition to U.S. support for Israel, military presence in Saudi Arabia and the Middle East, sanctions against Iraq, and perceived repression of Muslims worldwide. Bin Laden declared the attacks as retaliatory strikes against American policies and actions considered aggressive or oppressive toward Muslims. The attacks aimed to target symbols of U.S. economic and military power, provoke an American response, and rally support for Islamist militancy.
In summary, "they did 9" (the 9/11 attacks) because al-Qaeda sought to challenge and retaliate against what they perceived as harmful U.S. foreign policies, and to strike a symbolic and devastating blow to American power.
If more specific detail is desired about any aspect, please specify.
