The September 11 attacks, commonly known as 9/11, were four coordinated Islamist suicide terrorist attacks carried out by al-Qaeda against the United States on September 11, 2001. That morning, 19 terrorists hijacked four commercial airliners scheduled to travel from the East Coast to California. The hijackers crashed the first two planes into the Twin Towers of the World Trade Center in New York City, two of the world's five tallest buildings at the time, and aimed the next two flights toward targets in or near Washington, D.C., in an attack on the nation's capital. The third team succeeded in striking the Pentagon, the headquarters of the U.S. Department of Defense in Arlington County, Virginia, while the fourth plane crashed in rural Pennsylvania during a passenger revolt. The September 11 attacks killed 2,977 people, making them the deadliest terrorist attack in history, and instigated the multi-decade global war on terror, fought in Afghanistan, Iraq, and elsewhere.

Islamism is a religio-political ideology. The advocates of Islamism, also known as "al-Islamiyyun", are dedicated to realizing their ideological interpretation of Islam within the context of the state or society. The majority of them are affiliated with Islamic institutions or social mobilization movements, often designated as "al-harakat al-Islamiyyah." Islamists emphasize the implementation of sharia, pan-Islamic political unity, the creation of Islamic states,, and rejection of non-Muslim influences—particularly Western or universal economic, military, political, social, or cultural.