While Obama did not explicitly mention the crisis in Syria or the standoff over Bashar al-Assad's chemical weapons, he did make fleeting reference to the need to sometimes give diplomacy a chance when confronting threats to U.S. security.
"As long as there are those who would strike our citizens, we will stand vigilant and defend our nation," Obama said. "Let us have the wisdom to know that while force is at times necessary, force alone cannot build the world we seek."
In a rare prime-time address to the nation on Tuesday, Obama said he was delaying a push for a congressional vote on U.S. military force against Syria to allow time to explore a Russian proposal that would disarm the regime and put its chemcial weapons stockpiles under international control.
There have been three successful terror attacks against the U.S. on President Obama's watch. In addition to Benghazi, two al Qaeda-inspired men killed three and injured dozens of others earlier this year in an attack at the Boston Marathon. In 2009, Maj. Nidal Hassan, an avowed jihadist with ties to Anwar al-Awlaki, went on a shooting spree at Fort Hood, Texas, killing 13 and injuring 30.
The Obamas have called for Sept. 11 -- now known as Patriot Day -- to be a national day of service and remembrance. Both the president and first lady will participate in acts of service in the Washington, D.C., area.
Mrs. Obama will visit with military children and their families at the USO Warrior and Family Center at Ft. Belvoir. The president will separately join a service project.
"Let us have the confidence in the values that make us Americans, which we must never lose, the shining liberties that make us a beacon to the world, the rich diversity that makes us stronger, the unity and commitment to one another that we sustain on this national day of service and remembrance," Obama said at the Pentagon.
At the Pentagon, more than a thousand Department of Defense employees attended Wednesday afternoon's Sept. 11 remembrance ceremony hosted by Defense Secretary Hagel and Joint Chiefs Chairman Gen. Martin Dempsey.
Hagel said Pentagon employees are aware of the legacy of courage and resilience exhibited on that day 12 years ago, which continue to be a source of strength and pride for all who serve at the Pentagon. His remarks seemed to touch on Syria without actually mentioning it. He said a critical living lesson learned from Sept. 11 is that the U.S. is not insulated from the events and threats that occur in the rest of the world. Hagel said these events "matter profoundly" and "if we don't act in the face of threats to our national interests and our future, there are consequences."
In another veiled reference to Syria he added, "we must be vigilant, we must always stay ahead of emerging challenges and threats, and we must take action, but wise action -- wise action -- when necessary to defend our interests and our country. "
"These are not easy times. These are complicated times. The world is growing more complex, interconnected, more combustible. But America and the world have within our grasp the potential to do more good for more people than the world has ever known," Hagel said. "And whether we fulfill that promise depends on many ways. It depends on us, and it depends on our dedication and the continued dedication of the men and women who are here today."
Dempsey's remarks focused on the resilience and resolve forged by America in the dozen years since the attacks. He praised the "quiet heroism" exhibited by the Pentagon workforce.
"It's the spirit and pride that permeates these hallways," Dempsey said. "You're devoted to an uncommon profession, a calling that is bigger than yourselves."
Meanwhile, on Capitol Hill, many observers took photos of the lawmakers gathered together in remembrance, capturing a rare snapshot of a divided Congress locked in unity while the U.S. flag flew above them at half-staff.
"Twelve years ago our nation was shaken, our hearts were broken, and our country came together," House Minority Leader Nancy Pelosi, D-Calif., said. "All of us remember where we were when the twin towers fell, when the Pentagon was struck, when Flight 93 was brought down in Pennsylvania. All of us remember the horrific images of that clear morning: the destruction and devastation, the tragedy and fear, the unimaginable loss." "We look back today with our hearts still heavy and our heads still bowed," Senate Minority Leader Mitch McConnell, R-Ky., added. "We say again that you will never be forgotten."
Senate Majority Leader Harry Reid recounted the day of the attacks, from the time he rushed out of the U.S. Capitol when law enforcement believed the building was the next target to the moment Sen. Barbara Mikulski, D-Md., suggested lawmakers join together to sing "God Bless America" outside the U.S. Capitol.
"I will never forget 12 years ago," Reid promised before the ceremony concluded, once again, with the singing of "God Bless America."