2. The September 11 Attacks (2001)
On September 11, 2001, a series of coordinated terrorist attacks on the United States stunned the world. Four hijacked planes crashed into the World Trade Center, the Pentagon, and a Pennsylvania field, causing massive loss of life and destruction. The sheer scale and suddenness of the attacks left people everywhere in disbelief. In a single morning, global priorities shifted, leading to sweeping changes in security and foreign policy. As History.com notes, the world would never be the same after that fateful day.
