Twenty-three years have passed since the attacks of September 11, 2001, and on Wednesday Pentagon leaders will pause and reflect on a day marked by tragedy and heroism.

The attacks killed nearly 3,000 people, including 184 people when a hijacked plane crashed into the U.S. Department of Defense headquarters in Arlington, Virginia.

“I am honored to join you in fulfilling our promise to never forget what happened on this day and in this place, and to honor those we lost,” Deputy Secretary of Defense Kathleen Hicks said during a memorial ceremony Tuesday. “What remains with me more than two decades later is the collective resolve and resilience that this nation can and has shown in the face of horrific violence.”

As a sign of its resilience, the Pentagon unfurled an American flag over the building at sunrise on Wednesday.

Secretary of Defense Lloyd Austin and Gen. Charles Q. Brown, chairman of the Joint Chiefs of Staff, will speak at a ceremony honoring the deceased. The ceremony is scheduled to begin at 9 a.m. On this page you can follow the memorial ceremony at the Pentagon live.

In New York and Shanksville (Pennsylvania) memorial ceremonies for the victims also began early.

Across the country, thousands of volunteers honor the courage and sacrifice of that day by beautifying dozens of American military cemeteries.