What major event occurred on September 11, 2001?

The major event that occurred on September 11, 2001, was a terrorist attack on the World Trade Center and The Pentagon. This date is significant in history as it marked a coordinated assault by the extremist group al-Qaeda, resulting in the deaths of nearly 3,000 people and extensive destruction. The attacks involved the hijacking of four commercial airplanes, two of which were flown into the Twin Towers of the World Trade Center in New York City, causing both towers to collapse, while another struck The Pentagon, the headquarters of the United States Department of Defense.

This event had profound implications for U.S. and global security, leading to increased counter-terrorism efforts, significant changes in U.S. foreign policy, and the initiation of the War on Terror, including military engagements in Afghanistan and Iraq. The impact of this day continues to shape international relations and national security protocols. Other options provided do not reflect events of that specific date and context, emphasizing the uniqueness and significance of the September 11 attacks in contemporary history.